Last autumn, there was a military coup in Thailand. The leaders of the coup took a number of steps, rather systematically, as if they had a shopping list. In a sense, they did. Within a matter of days, democracy had been closed down: the coup leaders declared martial law, sent armed soldiers into residential areas, took over radio and TV stations, issued restrictions on the press, tightened some limits on travel, and took certain activists into custody. They were not figuring these things out as they went along. If you look at history, you can see that there is essentially a blueprint for turning an open society into a dictatorship. That blueprint has been used again and again in more and less bloody, more and less terrifying ways. But it is always effective. It is very difficult and arduous to create and sustain a democracy - but history shows that closing one down is much simpler. You simply have to be willing to take the 10 steps.

As difficult as this is to contemplate, it is clear, if you are willing to look, that each of these 10 steps has already been initiated today in the United States by the Bush administration.

Because Americans like me were born in freedom, we have a hard time even considering that it is possible for us to become as unfree - domestically - as many other nations. Because we no longer learn much about our rights or our system of government - the task of being aware of the constitution has been outsourced from citizens' ownership to being the domain of professionals such as lawyers and professors - we scarcely recognise the checks and balances that the founders put in place, even as they are being systematically dismantled. Because we don't learn much about European history, the setting up of a department of "homeland" security - remember who else was keen on the word "homeland" - didn't raise the alarm bells it might have.

It is my argument that, beneath our very noses, George Bush and his administration are using time-tested tactics to close down an open society. It is time for us to be willing to think the unthinkable - as the author and political journalist Joe Conason, has put it, that it can happen here. And that we are further along than we realise.

Conason eloquently warned of the danger of American authoritarianism. I am arguing that we need also to look at the lessons of European and other kinds of fascism to understand the potential seriousness of the events we see unfolding in the US.

1. Invoke a terrifying internal and external enemy

After we were hit on September 11 2001, we were in a state of national shock. Less than six weeks later, on October 26 2001, the USA Patriot Act was passed by a Congress that had little chance to debate it; many said that they scarcely had time to read it. We were told we were now on a "war footing"; we were in a "global war" against a "global caliphate" intending to "wipe out civilisation". There have been other times of crisis in which the US accepted limits on civil liberties, such as during the civil war, when Lincoln declared martial law, and the second world war, when thousands of Japanese-American citizens were interned. But this situation, as Bruce Fein of the American Freedom Agenda notes, is unprecedented: all our other wars had an endpoint, so the pendulum was able to swing back toward freedom; this war is defined as open-ended in time and without national boundaries in space - the globe itself is the battlefield. "This time," Fein says, "there will be no defined end."

Creating a terrifying threat - hydra-like, secretive, evil - is an old trick. It can, like Hitler's invocation of a communist threat to the nation's security, be based on actual events (one Wisconsin academic has faced calls for his dismissal because he noted, among other things, that the alleged communist arson, the Reichstag fire of February 1933, was swiftly followed in Nazi Germany by passage of the Enabling Act, which replaced constitutional law with an open-ended state of emergency). Or the terrifying threat can be based, like the National Socialist evocation of the "global conspiracy of world Jewry", on myth.

It is not that global Islamist terrorism is not a severe danger; of course it is. I am arguing rather that the language used to convey the nature of the threat is different in a country such as Spain - which has also suffered violent terrorist attacks - than it is in America. Spanish citizens know that they face a grave security threat; what we as American citizens believe is that we are potentially threatened with the end of civilisation as we know it. Of course, this makes us more willing to accept restrictions on our freedoms.

2. Create a gulag

Once you have got everyone scared, the next step is to create a prison system outside the rule of law (as Bush put it, he wanted the American detention centre at Guantánamo Bay to be situated in legal "outer space") - where torture takes place.

At first, the people who are sent there are seen by citizens as outsiders: troublemakers, spies, "enemies of the people" or "criminals". Initially, citizens tend to support the secret prison system; it makes them feel safer and they do not identify with the prisoners. But soon enough, civil society leaders - opposition members, labour activists, clergy and journalists - are arrested and sent there as well.

This process took place in fascist shifts or anti-democracy crackdowns ranging from Italy and Germany in the 1920s and 1930s to the Latin American coups of the 1970s and beyond. It is standard practice for closing down an open society or crushing a pro-democracy uprising.

With its jails in Iraq and Afghanistan, and, of course, Guantánamo in Cuba, where detainees are abused, and kept indefinitely without trial and without access to the due process of the law, America certainly has its gulag now. Bush and his allies in Congress recently announced they would issue no information about the secret CIA "black site" prisons throughout the world, which are used to incarcerate people who have been seized off the street.

Gulags in history tend to metastasise, becoming ever larger and more secretive, ever more deadly and formalised. We know from first-hand accounts, photographs, videos and government documents that people, innocent and guilty, have been tortured in the US-run prisons we are aware of and those we can't investigate adequately.

But Americans still assume this system and detainee abuses involve only scary brown people with whom they don't generally identify. It was brave of the conservative pundit William Safire to quote the anti-Nazi pastor Martin Niemöller, who had been seized as a political prisoner: "First they came for the Jews." Most Americans don't understand yet that the destruction of the rule of law at Guantánamo set a dangerous precedent for them, too.

By the way, the establishment of military tribunals that deny prisoners due process tends to come early on in a fascist shift. Mussolini and Stalin set up such tribunals. On April 24 1934, the Nazis, too, set up the People's Court, which also bypassed the judicial system: prisoners were held indefinitely, often in isolation, and tortured, without being charged with offences, and were subjected to show trials. Eventually, the Special Courts became a parallel system that put pressure on the regular courts to abandon the rule of law in favour of Nazi ideology when making decisions.

3. Develop a thug caste

When leaders who seek what I call a "fascist shift" want to close down an open society, they send paramilitary groups of scary young men out to terrorise citizens. The Blackshirts roamed the Italian countryside beating up communists; the Brownshirts staged violent rallies throughout Germany. This paramilitary force is especially important in a democracy: you need citizens to fear thug violence and so you need thugs who are free from prosecution.

The years following 9/11 have proved a bonanza for America's security contractors, with the Bush administration outsourcing areas of work that traditionally fell to the US military. In the process, contracts worth hundreds of millions of dollars have been issued for security work by mercenaries at home and abroad. In Iraq, some of these contract operatives have been accused of involvement in torturing prisoners, harassing journalists and firing on Iraqi civilians. Under Order 17, issued to regulate contractors in Iraq by the one-time US administrator in Baghdad, Paul Bremer, these contractors are immune from prosecution

Yes, but that is in Iraq, you could argue; however, after Hurricane Katrina, the Department of Homeland Security hired and deployed hundreds of armed private security guards in New Orleans. The investigative journalist Jeremy Scahill interviewed one unnamed guard who reported having fired on unarmed civilians in the city. It was a natural disaster that underlay that episode - but the administration's endless war on terror means ongoing scope for what are in effect privately contracted armies to take on crisis and emergency management at home in US cities.

Thugs in America? Groups of angry young Republican men, dressed in identical shirts and trousers, menaced poll workers counting the votes in Florida in 2000. If you are reading history, you can imagine that there can be a need for "public order" on the next election day. Say there are protests, or a threat, on the day of an election; history would not rule out the presence of a private security firm at a polling station "to restore public order".

4. Set up an internal surveillance system

In Mussolini's Italy, in Nazi Germany, in communist East Germany, in communist China - in every closed society - secret police spy on ordinary people and encourage neighbours to spy on neighbours. The Stasi needed to keep only a minority of East Germans under surveillance to convince a majority that they themselves were being watched.

In 2005 and 2006, when James Risen and Eric Lichtblau wrote in the New York Times about a secret state programme to wiretap citizens' phones, read their emails and follow international financial transactions, it became clear to ordinary Americans that they, too, could be under state scrutiny.

In closed societies, this surveillance is cast as being about "national security"; the true function is to keep citizens docile and inhibit their activism and dissent.

5. Harass citizens' groups

The fifth thing you do is related to step four - you infiltrate and harass citizens' groups. It can be trivial: a church in Pasadena, whose minister preached that Jesus was in favour of peace, found itself being investigated by the Internal Revenue Service, while churches that got Republicans out to vote, which is equally illegal under US tax law, have been left alone.

Other harassment is more serious: the American Civil Liberties Union reports that thousands of ordinary American anti-war, environmental and other groups have been infiltrated by agents: a secret Pentagon database includes more than four dozen peaceful anti-war meetings, rallies or marches by American citizens in its category of 1,500 "suspicious incidents". The equally secret Counterintelligence Field Activity (Cifa) agency of the Department of Defense has been gathering information about domestic organisations engaged in peaceful political activities: Cifa is supposed to track "potential terrorist threats" as it watches ordinary US citizen activists. A little-noticed new law has redefined activism such as animal rights protests as "terrorism". So the definition of "terrorist" slowly expands to include the opposition.

6. Engage in arbitrary detention and release

This scares people. It is a kind of cat-and-mouse game. Nicholas D Kristof and Sheryl WuDunn, the investigative reporters who wrote China Wakes: the Struggle for the Soul of a Rising Power, describe pro-democracy activists in China, such as Wei Jingsheng, being arrested and released many times. In a closing or closed society there is a "list" of dissidents and opposition leaders: you are targeted in this way once you are on the list, and it is hard to get off the list.

In 2004, America's Transportation Security Administration confirmed that it had a list of passengers who were targeted for security searches or worse if they tried to fly. People who have found themselves on the list? Two middle-aged women peace activists in San Francisco; liberal Senator Edward Kennedy; a member of Venezuela's government - after Venezuela's president had criticised Bush; and thousands of ordinary US citizens.

Professor Walter F Murphy is emeritus of Princeton University; he is one of the foremost constitutional scholars in the nation and author of the classic Constitutional Democracy. Murphy is also a decorated former marine, and he is not even especially politically liberal. But on March 1 this year, he was denied a boarding pass at Newark, "because I was on the Terrorist Watch list".

"Have you been in any peace marches? We ban a lot of people from flying because of that," asked the airline employee.

"I explained," said Murphy, "that I had not so marched but had, in September 2006, given a lecture at Princeton, televised and put on the web, highly critical of George Bush for his many violations of the constitution."

"That'll do it," the man said.

Anti-war marcher? Potential terrorist. Support the constitution? Potential terrorist. History shows that the categories of "enemy of the people" tend to expand ever deeper into civil life.

James Yee, a US citizen, was the Muslim chaplain at Guantánamo who was accused of mishandling classified documents. He was harassed by the US military before the charges against him were dropped. Yee has been detained and released several times. He is still of interest.

Brandon Mayfield, a US citizen and lawyer in Oregon, was mistakenly identified as a possible terrorist. His house was secretly broken into and his computer seized. Though he is innocent of the accusation against him, he is still on the list.

It is a standard practice of fascist societies that once you are on the list, you can't get off.

7. Target key individuals

Threaten civil servants, artists and academics with job loss if they don't toe the line. Mussolini went after the rectors of state universities who did not conform to the fascist line; so did Joseph Goebbels, who purged academics who were not pro-Nazi; so did Chile's Augusto Pinochet; so does the Chinese communist Politburo in punishing pro-democracy students and professors.

Academe is a tinderbox of activism, so those seeking a fascist shift punish academics and students with professional loss if they do not "coordinate", in Goebbels' term, ideologically. Since civil servants are the sector of society most vulnerable to being fired by a given regime, they are also a group that fascists typically "coordinate" early on: the Reich Law for the Re-establishment of a Professional Civil Service was passed on April 7 1933.

Bush supporters in state legislatures in several states put pressure on regents at state universities to penalise or fire academics who have been critical of the administration. As for civil servants, the Bush administration has derailed the career of one military lawyer who spoke up for fair trials for detainees, while an administration official publicly intimidated the law firms that represent detainees pro bono by threatening to call for their major corporate clients to boycott them.

Elsewhere, a CIA contract worker who said in a closed blog that "waterboarding is torture" was stripped of the security clearance she needed in order to do her job.

Most recently, the administration purged eight US attorneys for what looks like insufficient political loyalty. When Goebbels purged the civil service in April 1933, attorneys were "coordinated" too, a step that eased the way of the increasingly brutal laws to follow.

8. Control the press

Italy in the 1920s, Germany in the 30s, East Germany in the 50s, Czechoslovakia in the 60s, the Latin American dictatorships in the 70s, China in the 80s and 90s - all dictatorships and would-be dictators target newspapers and journalists. They threaten and harass them in more open societies that they are seeking to close, and they arrest them and worse in societies that have been closed already.

The Committee to Protect Journalists says arrests of US journalists are at an all-time high: Josh Wolf (no relation), a blogger in San Francisco, has been put in jail for a year for refusing to turn over video of an anti-war demonstration; Homeland Security brought a criminal complaint against reporter Greg Palast, claiming he threatened "critical infrastructure" when he and a TV producer were filming victims of Hurricane Katrina in Louisiana. Palast had written a bestseller critical of the Bush administration.

Other reporters and writers have been punished in other ways. Joseph C Wilson accused Bush, in a New York Times op-ed, of leading the country to war on the basis of a false charge that Saddam Hussein had acquired yellowcake uranium in Niger. His wife, Valerie Plame, was outed as a CIA spy - a form of retaliation that ended her career.

Prosecution and job loss are nothing, though, compared with how the US is treating journalists seeking to cover the conflict in Iraq in an unbiased way. The Committee to Protect Journalists has documented multiple accounts of the US military in Iraq firing upon or threatening to fire upon unembedded (meaning independent) reporters and camera operators from organisations ranging from al-Jazeera to the BBC. While westerners may question the accounts by al-Jazeera, they should pay attention to the accounts of reporters such as the BBC's Kate Adie. In some cases reporters have been wounded or killed, including ITN's Terry Lloyd in 2003. Both CBS and the Associated Press in Iraq had staff members seized by the US military and taken to violent prisons; the news organisations were unable to see the evidence against their staffers.

Over time in closing societies, real news is supplanted by fake news and false documents. Pinochet showed Chilean citizens falsified documents to back up his claim that terrorists had been about to attack the nation. The yellowcake charge, too, was based on forged papers.

You won't have a shutdown of news in modern America - it is not possible. But you can have, as Frank Rich and Sidney Blumenthal have pointed out, a steady stream of lies polluting the news well. What you already have is a White House directing a stream of false information that is so relentless that it is increasingly hard to sort out truth from untruth. In a fascist system, it's not the lies that count but the muddying. When citizens can't tell real news from fake, they give up their demands for accountability bit by bit.

9. Dissent equals treason

Cast dissent as "treason" and criticism as "espionage'. Every closing society does this, just as it elaborates laws that increasingly criminalise certain kinds of speech and expand the definition of "spy" and "traitor". When Bill Keller, the publisher of the New York Times, ran the Lichtblau/Risen stories, Bush called the Times' leaking of classified information "disgraceful", while Republicans in Congress called for Keller to be charged with treason, and rightwing commentators and news outlets kept up the "treason" drumbeat. Some commentators, as Conason noted, reminded readers smugly that one penalty for violating the Espionage Act is execution.

Conason is right to note how serious a threat that attack represented. It is also important to recall that the 1938 Moscow show trial accused the editor of Izvestia, Nikolai Bukharin, of treason; Bukharin was, in fact, executed. And it is important to remind Americans that when the 1917 Espionage Act was last widely invoked, during the infamous 1919 Palmer Raids, leftist activists were arrested without warrants in sweeping roundups, kept in jail for up to five months, and "beaten, starved, suffocated, tortured and threatened with death", according to the historian Myra MacPherson. After that, dissent was muted in America for a decade.

In Stalin's Soviet Union, dissidents were "enemies of the people". National Socialists called those who supported Weimar democracy "November traitors".

And here is where the circle closes: most Americans do not realise that since September of last year - when Congress wrongly, foolishly, passed the Military Commissions Act of 2006 - the president has the power to call any US citizen an "enemy combatant". He has the power to define what "enemy combatant" means. The president can also delegate to anyone he chooses in the executive branch the right to define "enemy combatant" any way he or she wants and then seize Americans accordingly.

Even if you or I are American citizens, even if we turn out to be completely innocent of what he has accused us of doing, he has the power to have us seized as we are changing planes at Newark tomorrow, or have us taken with a knock on the door; ship you or me to a navy brig; and keep you or me in isolation, possibly for months, while awaiting trial. (Prolonged isolation, as psychiatrists know, triggers psychosis in otherwise mentally healthy prisoners. That is why Stalin's gulag had an isolation cell, like Guantánamo's, in every satellite prison. Camp 6, the newest, most brutal facility at Guantánamo, is all isolation cells.)

We US citizens will get a trial eventually - for now. But legal rights activists at the Center for Constitutional Rights say that the Bush administration is trying increasingly aggressively to find ways to get around giving even US citizens fair trials. "Enemy combatant" is a status offence - it is not even something you have to have done. "We have absolutely moved over into a preventive detention model - you look like you could do something bad, you might do something bad, so we're going to hold you," says a spokeswoman of the CCR.

Most Americans surely do not get this yet. No wonder: it is hard to believe, even though it is true. In every closing society, at a certain point there are some high-profile arrests - usually of opposition leaders, clergy and journalists. Then everything goes quiet. After those arrests, there are still newspapers, courts, TV and radio, and the facades of a civil society. There just isn't real dissent. There just isn't freedom. If you look at history, just before those arrests is where we are now.

10. Suspend the rule of law

The John Warner Defense Authorization Act of 2007 gave the president new powers over the national guard. This means that in a national emergency - which the president now has enhanced powers to declare - he can send Michigan's militia to enforce a state of emergency that he has declared in Oregon, over the objections of the state's governor and its citizens.

Even as Americans were focused on Britney Spears's meltdown and the question of who fathered Anna Nicole's baby, the New York Times editorialised about this shift: "A disturbing recent phenomenon in Washington is that laws that strike to the heart of American democracy have been passed in the dead of night ... Beyond actual insurrection, the president may now use military troops as a domestic police force in response to a natural disaster, a disease outbreak, terrorist attack or any 'other condition'."

Critics see this as a clear violation of the Posse Comitatus Act - which was meant to restrain the federal government from using the military for domestic law enforcement. The Democratic senator Patrick Leahy says the bill encourages a president to declare federal martial law. It also violates the very reason the founders set up our system of government as they did: having seen citizens bullied by a monarch's soldiers, the founders were terrified of exactly this kind of concentration of militias' power over American people in the hands of an oppressive executive or faction.

Of course, the United States is not vulnerable to the violent, total closing-down of the system that followed Mussolini's march on Rome or Hitler's roundup of political prisoners. Our democratic habits are too resilient, and our military and judiciary too independent, for any kind of scenario like that.

Rather, as other critics are noting, our experiment in democracy could be closed down by a process of erosion.

It is a mistake to think that early in a fascist shift you see the profile of barbed wire against the sky. In the early days, things look normal on the surface; peasants were celebrating harvest festivals in Calabria in 1922; people were shopping and going to the movies in Berlin in 1931. Early on, as WH Auden put it, the horror is always elsewhere - while someone is being tortured, children are skating, ships are sailing: "dogs go on with their doggy life ... How everything turns away/ Quite leisurely from the disaster."

As Americans turn away quite leisurely, keeping tuned to internet shopping and American Idol, the foundations of democracy are being fatally corroded. Something has changed profoundly that weakens us unprecedentedly: our democratic traditions, independent judiciary and free press do their work today in a context in which we are "at war" in a "long war" - a war without end, on a battlefield described as the globe, in a context that gives the president - without US citizens realising it yet - the power over US citizens of freedom or long solitary incarceration, on his say-so alone.

That means a hollowness has been expanding under the foundation of all these still- free-looking institutions - and this foundation can give way under certain kinds of pressure. To prevent such an outcome, we have to think about the "what ifs".

What if, in a year and a half, there is another attack - say, God forbid, a dirty bomb? The executive can declare a state of emergency. History shows that any leader, of any party, will be tempted to maintain emergency powers after the crisis has passed. With the gutting of traditional checks and balances, we are no less endangered by a President Hillary than by a President Giuliani - because any executive will be tempted to enforce his or her will through edict rather than the arduous, uncertain process of democratic negotiation and compromise.

What if the publisher of a major US newspaper were charged with treason or espionage, as a rightwing effort seemed to threaten Keller with last year? What if he or she got 10 years in jail? What would the newspapers look like the next day? Judging from history, they would not cease publishing; but they would suddenly be very polite.

Right now, only a handful of patriots are trying to hold back the tide of tyranny for the rest of us - staff at the Center for Constitutional Rights, who faced death threats for representing the detainees yet persisted all the way to the Supreme Court; activists at the American Civil Liberties Union; and prominent conservatives trying to roll back the corrosive new laws, under the banner of a new group called the American Freedom Agenda. This small, disparate collection of people needs everybody's help, including that of Europeans and others internationally who are willing to put pressure on the administration because they can see what a US unrestrained by real democracy at home can mean for the rest of the world.

We need to look at history and face the "what ifs". For if we keep going down this road, the "end of America" could come for each of us in a different way, at a different moment; each of us might have a different moment when we feel forced to look back and think: that is how it was before - and this is the way it is now.

"The accumulation of all powers, legislative, executive, and judiciary, in the same hands ... is the definition of tyranny," wrote James Madison. We still have the choice to stop going down this road; we can stand our ground and fight for our nation, and take up the banner the founders asked us to carry.

· Naomi Wolf's The End of America: A Letter of Warning to a Young Patriot will be published by Chelsea Green in September.