It was the "Mission Accomplished" of George Bush's second term, and an announcement of that magnitude called for a suitably dramatic location. But what was the right backdrop for the infamous "We do not torture" declaration? With characteristic audacity, the Bush team settled on downtown Panama City.

It was certainly bold. An hour and a half's drive from where Bush stood, the US military ran the notorious School of the Americas from 1946 to 1984, a sinister educational institution that, if it had a motto, might have been "We do torture". It is here in Panama, and later at the school's new location in Fort Benning, Georgia, where the roots of the current torture scandals can be found.

According to declassified training manuals, SOA students - military and police officers from across the hemisphere - were instructed in many of the same "coercive interrogation" techniques that have since gone to Guantánamo and Abu Ghraib: early morning capture to maximise shock, immediate hooding and blindfolding, forced nudity, sensory deprivation, sensory overload, sleep and food "manipulation", humiliation, extreme temperatures, isolation, stress positions - and worse. In 1996 President Clinton's Intelligence Oversight Board admitted that US-produced training materials condoned "execution of guerrillas, extortion, physical abuse, coercion and false imprisonment".

Some Panama school graduates went on to commit the continent's greatest war crimes of the past half-century: the murders of Archbishop Oscar Romero and six Jesuit priests in El Salvador; the systematic theft of babies from Argentina's "disappeared" prisoners; the massacre of 900 civilians in El Mozote in El Salvador; and military coups too numerous to list here.

Yet when covering the Bush announcement, not a single mainstream news outlet mentioned the location's sordid history. How could they? That would require something totally absent from the debate: an admission that the embrace of torture by US officials has been integral to US foreign policy since the Vietnam war.

It's a history exhaustively documented in an avalanche of books, declassified documents, CIA training manuals, court records and truth commissions. In his forthcoming book, A Question of Torture, Alfred McCoy synthesises this evidence, producing a riveting account of how monstrous CIA-funded experiments on psychiatric patients and prisoners in the 1950s turned into a template for what he calls "no-touch torture", based on sensory deprivation and self-inflicted pain. McCoy traces how these methods were field-tested by CIA agents in Vietnam as part of the Phoenix programme and then imported to Latin America and Asia under the guise of police training.

It is not only apologists for torture who ignore this history when they blame abuses on "a few bad apples". A startling number of torture's most prominent opponents keep telling us that the idea of torturing prisoners first occurred to US officials on September 11 2001, at which point the methods used in Guantánamo apparently emerged, fully formed, from the sadistic recesses of Dick Cheney's and Donald Rumsfeld's brains. Up until that moment, we are told, America fought its enemies while keeping its humanity intact.

The principal propagator of this narrative (what Garry Wills termed "original sinlessness") is Senator John McCain. Writing in Newsweek on the need to ban torture, McCain says that when he was a prisoner of war in Hanoi, he held fast to the knowledge "that we were different from our enemies ... that we, if the roles were reversed, would not disgrace ourselves by committing or approving such mistreatment of them". It is a stunning historical distortion. By the time McCain was taken captive, the CIA had launched the Phoenix programme and, as McCoy writes, "its agents were operating 40 interrogation centres in South Vietnam that killed more than 20,000 suspects and tortured thousands more."

Does it somehow lessen today's horrors to admit that this is not the first time the US government has used torture, that it has operated secret prisons before, that it has actively supported regimes that tried to erase the left by dropping students out of airplanes? That, closer to home, photographs of lynchings were traded and sold as trophies and warnings? Many seem to think so. On November 8, Democratic Congressman Jim McDermott made the astonishing claim to the House of Representatives that "America has never had a question about its moral integrity, until now".

Other cultures deal with a legacy of torture by declaring "Never again!" Why do so many Americans insist on dealing with the current torture crisis by crying "Never before"? I suspect it stems from a sincere desire to convey the seriousness of this administration's crimes. And its open embrace of torture is indeed unprecedented.

But let's be clear about what is unprecedented: not the torture, but the openness. Past administrations kept their "black ops" secret; the crimes were sanctioned but they were committed in the shadows, officially denied and condemned. The Bush administration has broken this deal: post-9/11, it demanded the right to torture without shame, legitimised by new definitions and new laws.

Despite all the talk of outsourced torture, the real innovation has been in-sourcing, with prisoners being abused by US citizens in US-run prisons and transported to third countries in US planes. It is this departure from clandestine etiquette that has so much of the military and intelligence community up in arms: Bush has robbed everyone of plausible deniability. This shift is of huge significance. When torture is covertly practised but officially and legally repudiated, there is still hope that if atrocities are exposed, justice could prevail. When torture is pseudo-legal and those responsible deny that it is torture, what dies is what Hannah Arendt called "the juridical person in man". Soon victims no longer bother to search for justice, so sure are they of the futility, and danger, of that quest. This is a larger mirror of what happens inside the torture chamber, when prisoners are told they can scream all they want because no one can hear them and no one is going to save them.

The terrible irony of the anti-historicism of the torture debate is that in the name of eradicating future abuses, past crimes are being erased from the record. Since the US has never had truth commissions, the memory of its complicity in far-away crimes has always been fragile. Now these memories are fading further, and the disappeared are disappearing again.

This casual amnesia does a disservice not only to the victims, but also to the cause of trying to remove torture from the US policy arsenal once and for all. Already there are signs that the administration will deal with the uproar by returning to plausible deniability. The McCain amendment protects every "individual in the custody or under the physical control of the United States government"; it says nothing about torture training or buying information from the exploding industry of for-profit interrogators.

And in Iraq the dirty work is already being handed over to Iraqi death squads, trained by the US and supervised by commanders like Jim Steele, who prepared for the job by setting up similar units in El Salvador. The US role in training and supervising Iraq's interior ministry was forgotten, moreover, when 173 prisoners were recently discovered in a ministry dungeon, some tortured so badly that their skin was falling off. "Look, it's a sovereign country. The Iraqi government exists," Rumsfeld said. He sounded just like the CIA's William Colby who, asked in a 1971 Congressional probe about the thousands killed under Phoenix, a programme he helped launch, replied that it was now "entirely a South Vietnamese programme".

As McCoy says, "if you don't understand the history and the depths of the institutional and public complicity, then you can't begin to undertake meaningful reforms." Lawmakers will respond to pressure by eliminating one small piece of the torture apparatus: closing a prison, shutting down a programme, even demanding the resignation of a really bad apple like Rumsfeld. But he warns, "they will preserve the prerogative to torture."