I do not think that Europeans, even now, completely understand what has happened to America. They saw the pictures, they know the numbers, they heard the President's vows to smoke bin Laden out of his cave, and his pledge to end world terrorism.
They mostly agree with their leaders' support for what Mr Bush is doing. They're aware we are all involved. They can imagine what the anthrax means. All the same, what they still miss, if they do not come here, is the quite awesome hardening of the American soul.
Before September 11th this was a mushy psychic space. Americans felt comfortable with themselves, and wanted no distractions. They were backing away from the world. Notoriously, their leaders didn't dare challenge the complacency zone by endangering a single American soldier. A body-bag count of zero set an inflexible limit round foreign policy. Bush came to power pledged, if possible, to minus zero.
Now quite suddenly America has become a warrior nation. Domestic politics which for years has been a force for inertia is now a force for action. I've spent several days asking people in Washington and New York about the political limits constraining Bush's ambition to wipe out terrorism.
It is, after all, a vast project: another sort of world war, the very model of an interventionist future such as Democrats, let alone Republicans, have rejected for a decade. Yet the limits, for the moment, seem remarkably few.
The military campaign in Afghanistan has virtually total support. So far Americans may know of little more than the bombing. So far the operation is as anaesthetic as Kosovo. But when the special forces go in, there will be no recoiling. The critical mass of outrage will see the struggle through until the capture of bin Laden.
No antsy-fancy squeamishness here. People who've travelled round the country say that feelings in the hinterland are even more war-minded - internationalist, you might say - than on the worldly east coast.
This isn't, they piously insist, a matter of revenge. But something like that is present, an emotion many Americans find easier to register than they did during Vietnam. Vietnam was war for a strategic theory few of them grasped, against an abstract enemy that had done them little visible harm, on distant soil most of them never hoped to visit.
Now the unforgettable fact of 5,000-plus souls being reduced to ashes before their eyes makes anything that now has to happen in response rather easy to support.
So a whole agenda is unfolding. Congress did trim the President's extreme request for imprisonment without trial for all suspected terrorists. But new surveillance and money-freezing measures are sweeping past. There's a mood of compliance with whatever needs to be done.
At a seminar of 30 distinguished liberal academics, I heard it asserted without contradiction that just one more major terrorist assault would supply carte blanche for repression against anyone who looked like a Muslim. In the mainstream media, liberals and conservatives alike ride their columns hard behind the leader.
Debate of many kinds has vanished, in this mood of national solidarity. On television, the big political players are soothed rather than interrogated. Puzzlement and shared gravitas is the keynote of discussion, victory the goal on which all are set - without the meaning of victory always being defined. The collateral damage to other arguments reaches far and wide.
Take the example of missile defence, or NMD. Far from September 11th making the case against this high-tech extravaganza, it proved that NMD must go ahead. Rogue states that sponsor terrorists are crazy enough to sponsor missile attack: every crevice of vulnerability must be closed: q.e.d., the space war must begin, as even the Democrats have stopped trying to deny.
This is not an invented national mood, got up by a handful of spin doctors for the convenience of the government. Nor is it born of anything so shallow as panic. London doesn't have sole call on the spirit of the Blitz, on which it congratulates itself with such embarrassing frequency, 60 years on, as if no other city is capable of grace under pressure.
New York has reinvented and redoubled that grace, waiting for the next anthrax booby trap or lorry-bomb. Americans are capable of just as much human stoicism, faced for the first time with this demand for it. They are fearful, but calmly so - and with a determination history has never quite seen before, for the reason that nothing quite like the present threat has ever faced Americans in their land.
In the end, I got a few answers to my question. All is not perfectly serene for Mr Bush. The public will remain behind him as long as he seems to know what he is doing. They may not demand victories now, but they need to see that Defence Secretary Donald Rumsfeld is measured in his bombing, and Secretary of State Colin Powell inventive in his diplomacy. So far, which has been the easy bit, these standards have been met.
With Congressional elections next year, bipartisanship cannot be relied on if there's a major blunder. There are tests also for the military campaign. The united solemnity I describe would not survive, for example, the failure to capture bin Laden in the three remaining years of Bush's term. Having personalised the enemy, he's bound to pay if the enemy survives. Another limit is set around the extended presence of an American army in Afghanistan. The American people would see no more sense in that than American generals. Other limits often discussed in Europe, however, are less imposing. Britain is the lead ally, and Tony Blair has supplanted Maggie Thatcher as the foreign politician most Americans wish they could vote for.
Sitting in London, one can nurture the impression that this is an allied enterprise in which kaleidoscopic global interests will have their say in a Washington desperate to keep them happy, especially when it comes to extending the anti-terror war all over the Middle East. Washington's desperation, in truth, is limited. It wants to keep its friends, but on its terms. In the old days, ambivalence attended every piece of active American foreign policy. America felt uneasy about her power, Americans anxious about the risks of intervention. That has all gone.
Not only will Bush feel weak if terrorism lives on, but his country will say a debt has not been repaid to the dead, and security not bestowed upon the living. America has the power, and now the nerve, to act alone. A new world is born, for friends as well as enemies uneasily to note.
Hugo Young is a commentator with the Guardian newspaper