On 19 November 2005 a US marine squad was struck by a roadside bomb in Haditha, in Iraq’s Anbar province, killing one soldier and seriously injuring two others. According to civilians they then went on the rampage, slaughtering 24 people.

They included a 76-year-old man in a wheelchair and a three-year-old child. It was a massacre. "I think they were just blinded by hate … and they just lost control," said James Crossan, one of the injured marines.

When he heard the news, Major General Steve Johnson, the American commander in Anbar province at the time, saw no cause for further examination.

"It happened all the time … throughout the whole country. So you know, maybe, if I was sitting here [in Virginia] and heard that 15 civilians were killed I would have been surprised and shocked and done more to look into it. But at that point in time I felt that it was just a cost of doing business on that particular engagement."

Eight soldiers were originally charged with the atrocity. Charges against six were dropped, one was acquitted and the other is awaiting trial. We know this because a New York Times reporter found documents from the US military’s internal investigation in a rubbish dump near Baghdad. An attendant was using them to make a fire to cook smoked carp for dinner.

The article ran on the same day that Barack Obama announced the withdrawal of American troops last week, hailing the almost nine-year war a "success", resulting in "an extraordinary achievement" that the troops can look on "with their heads held high". And so it is that America moves on, casting evidence of its war crimes in the trash, holding nobody accountable and choosing to understand defeat as victory and failure as success.

While the departure of American troops should be greeted with guarded relief (guarded because the US will maintain its largest embassy in the world there along with thousands of armed private contractors), every effort must be made to thwart those who seek to embellish and distort their lamentable legacy.

You’d think that would be easy. The case against this war has been prosecuted extensively both in this column and elsewhere. (The argument that the removal of Saddam Hussein somehow compensates for the lies, torture, displacement, carnage, instability and humans rights abuses is perverse. They used a daisy cutter to crack a walnut.)

This war started out with many parents but has ended its days an orphan, tarnishing the reputations of those who launched it and the useful idiots who gave them intellectual cover. Nobody has been held accountable; few accept responsibility.

In any case, they could not have done it alone. It was only possible thanks to the systemic collusion of a supine political class and a jingoistic political culture, not to mention a blank cheque from the British government. When the war started, almost three-quarters of Americans supported it. Only politicians of principle opposed it – and there were precious few of those.

When Nancy Pelosi was asked why she had not pushed for impeachment of Bush when she became speaker in 2006 she said: "What about these other people who voted for that war with no evidence … Where are these Democrats going to be? Are they going to be voting for us to impeach a president who took us to war on information that they had also?"

Today, withdrawing the troops is about the only truly popular thing Obama has done in the last two years. Polls show more than 70% support withdrawal, roughly two-thirds oppose the war, and more than half believe it was a mistake. But there is a difference between regretting something and learning from it. And while there is ample evidence of the former, there is little to suggest the latter.

According to Christopher Gelpi, a political science professor at Duke University who specialises in public attitudes to foreign policy, the most important single factor shaping Americans’ opinions about any war is whether they think America will win. This solipsistic worldview is hardly conducive to the kind of introspection that might translate remorse into redemption.

It’s a mindset that understands the war in Vietnam as being wrong not because an independent country was invaded, flattened, millions murdered and thousands tortured. It was wrong because the US lost.

And it pervades the political spectrum. Even when the war’s critics slam the blood and treasure squandered, they usually refer only to American lives and American money. This is also the way pollsters frame it. A recent CBS poll asked: "Do you think removing Saddam Hussein from power was worth the loss of American life and other costs of attacking Iraq, or not?" (50% no, 41% yes), and "Do you think the result of the war with Iraq was worth the loss of American lives and other costs of attacking Iraq, or not?" (67% no, 24% yes). The cost to Iraqis simply does not feature.

"It is the end for the Americans only," wrote Emad Risn, argued an Iraqi columnist in a government-funded newspaper. "Nobody knows if the war will end for Iraqis too." And few Americans seem to care. It’s been some time since Iraq featured at all on the nation’s priorities, let alone high. Rightly Americans fret about the fate of veterans returning to a depressed economy with a range of both physical and mental disabilities. But Iraqi civilians barely get a look-in.

According to the New York Times report, among the discarded testimony was an interview with Sergeant Major Edward Sax. "I had marines shoot children in cars, and deal with the marines individually, one on one, about it because they have a hard time dealing with that." When they told him they didn’t know there were children on board he told them they were not to blame, claiming killing would impose a lifelong burden on them.

Progressives, seeking to link the economic collapse to military misadventure, often argue that nation building should begin at home, not in Iraq, thereby – wittingly or not – transforming Iraqis in the public imagination from victims of illegal warfare to recipients of illicit welfare