They never learn, do they? US strategists genuinely thought that the people of Iraq would burn all their banknotes because of the pictures of Saddam Hussein on them, and that the US dollar would then become the pre-eminent currency in Iraq. Instead - surprise, surprise - Iraqis clung on to their money, the dollar failed to soar in value in Iraq, and the $20 payments made to each Iraqi plunged in value. Another strategic miscalculation.
Now we are in the midst of more potentially disastrous ones, in the long and the short term, too. The talk among politicians over Memorial Day weekend inevitably included that frightening word "destabilisation", this time over Iran. Some openly talked of aiding Iran's exiled mujahedin - just as the US financially supported Osama Bin Laden's mujahedin after the Soviet Union occupied Afghanistan, and just as it bolstered Saddam Hussein during the Iran-Iraq war. The hawks in the administration - notably our friend Donald Rumsfeld, the defence secretary - insist that Iran is knowingly sheltering al-Qaeda members, planning nuclear weapons, and so on.
Despite Dubbya's famous labelling of Iran as one of the three countries comprising an "axis of evil", relations between the US and Iran had seemed to be improving. Ever since the Islamic revolution in 1979, the two countries have had no diplomatic relations. But that changed, in practice if not in theory, after the 11 September 2001 atrocities. The US and Iran held secret talks in Geneva and New York under UN auspices, and Iranian co-operation increased during the invasion of Iraq.
Iran also covertly opposed the Taliban in Afghanistan, only to be rewarded with Bush's "axis of evil" accusation; now the US has broken off the secret talks, and is communicating with Tehran only through the media. Specifically, the US is now accusing Iran of harbouring Saif al Adel, al-Qaeda's security boss, Osama Bin Laden's son Saad, and Abu Musab al-Zarqawi, whom Washington accuses of being a Saddam henchman.
But the 12 May suicide bombings in Riyadh in which 34 people - including nine Americans - were killed, really gave the hawks the excuse they needed. Quoting "chatter" - the new buzzword here to describe supposed intelligence on terrorist movements - the likes of Rumsfeld accused Iran of sheltering the al-Qaeda terrorists who were believed to be responsible for the Saudi bombings.
Iran has responded by saying that in the past year it has handed over more than 500 suspected al-Qaeda terrorists; it has also said that a dozen or so al-Qaeda members are believed to be in northern Iran, but that it does not know if they are senior planners or junior members. The Iranian foreign minister, Kamal Kharrazi, says: "There is no reason for us to help this organisation."
We are now, nevertheless, told that the US has "made it clear" that it expects Iran to co-operate in the Saudi investigations. The administration is also airing a second complaint against Iran: that it is fomenting trouble in Iraq, attempting to - here's that word again - "destabilise" American rule there.
General Richard Myers, the chairman of the Joint Chiefs of Staff, says: "Some portions of Iranian-backed forces and organisations are in Iraq now, trying to influence events there to the coalition's detriment."
His boss, Rumsfeld, meanwhile wrote in the Wall Street Journal: "Assistance from Iraq's neighbours will be welcomed. Conversely, interference in Iraq by its neighbours or their proxies - including those whose objective is to remake Iraq in Iran's image - will not be accepted or permitted." In other words, a popular Islamic state such as Iran's will not be "accepted or permitted" to work in Iraq, despite American insistence that it wants to bring democracy to Iraq.
Here we come to the crunch. Iran's population is three times greater than Iraq's, and its territory almost three times as large. It regards itself as leader of the world's 120 million Shia Muslims, including those who form the majority in Iraq. And Iran has so far talked tough: its ambassador to the United Nations, Javad Zarif, says that Iran will not co-operate in an atmosphere of "the language of pressure".
Iran's foreign ministry spokesman Hamid Reza Asefi said last Tuesday: "We hope that wisdom and logic dominate the Americans' debate and they refrain from carrying out any interference in our affairs. Iran . . . won't hesitate even for a fraction of a moment to defend itself."
But that has not dampened the rhetoric here. Representative Porter Goss, the Republican chairman of the House intelligence committee, sees it all quite simply: "The trick in Iran is this. The good guys are trying to bring reform; the bad guys control the levers of power. Sorting the two apart and then isolating the bad guys and taking the levers of power away from them is what's got to happen." Er, yes. And Senator Joe Lieberman, a Democratic contender for the presidency next year, who almost out-hawks the Republican hawks, says there has to be "regime change" in Iran.
Thus the language of confrontation has escalated. "Iran said to be producing bio-weapons", says a stray headline in the Washington Post.
John Wolf, assistant secretary of state for non-proliferation, says that Iran has an "alarming, clandestine programme". Ironically, the International Atomic Energy Agency is set to inspect Iran this month and, if it finds the evidence, could rule it in violation of the Nuclear Non-Proliferation Treaty, signed by Iran in 1970. (There is little dispute that Iran has an enriched uranium programme, but it insists it is intended for energy production only; to add to the mix of portents, Russia is building Iran's nuclear energy programme.)
Senator Joe Biden, the now-respected senior Democrat on the Senate's foreign relations committee, whose career was ruined by plagiarising one of Neil Kinnock's speeches, is one of the few dissenting voices to the increasingly heated rhetoric. The US should "go slow" over Iran, he says. "I don't think we should be biting off more than we can chew right now."
However, the voice of moderation is a lonely one in Washington these days, once this administration gets the bit between its teeth.
So now we have a familiar pattern emerging: increasing threats, more authoritarian rhetoric. We have a State Department that, not withstanding Wolf's comments, is more and more disturbed by the ratcheting-up of the Pentagon's war talk amid accusations that Iran is meddling in Iraq, developing nuclear weapons, sheltering al-Qaeda members and sponsoring terrorism.
We have Iran vehemently protesting its innocence. We have high-level meetings of the administration on Iran, such as one last Tuesday. We have the White House press secretary, Ari Fleischer, saying that Iran is reacting to US demands "insufficiently". And we have the neoconservative hawks of Washington increasingly beating those drums of war.
Let us hope that, this time, caution will prevail.