Sixty years after the Western Alliance was forged in the heroic invasion of Nazi-occupied France, the US and its European allies are at odds as never before.
It's true that President Bush's just-finished swing through Western Europe seems to have been a success, at least of atmospherics. Somber ceremonies remembering the liberation of Rome and the D-Day invasion provided leaders an opportunity to reflect on the lessons of their shared history.
But this year's bitter squabbling about Iraq between the US, France, Germany, and other old friends may be a symptom of more profound disunity. Since the fall of the Soviet Union, Europe needs the US less - and the US is less interested in Europe. The longstanding allies have different levels of involvement in, and different purposes for, other regions of the world.
Going forward, the trick may be for the West to find ways to disagree without the rancor displayed in the past year. Otherwise, this weekend's amity will have been but a brief spot of sun in a long, slow decline.
"US-European relations are at or near a postwar low point," says Charles A. Kupchan, director of European studies at the Council on Foreign Relations.
At least this weekend's events did not hurt the cause of reconciliation. Large public protests about US policies in Iraq didn't materialize. Mr. Bush and French President Jacques Chirac did their best to try and get along, discovering, among other things, that they have a shared interest in cattle. (Mr. Bush has a ranch in Texas; Mr. Chirac was once a minister of agriculture and rural development.)
On substance, Bush and Chirac said they had made progress on a UN resolution on returning self-government to Iraq. Both US and French officials spoke positively of a move by interim Iraqi Prime Minister Iyad Allawi, who has proposed establishing committees throughout Iraq to negotiate understandings regarding the action of US and other foreign troops.
But Chirac, for all his pleasantries, made it clear that by no means did France now completely agree with the US on Iraq policy. Bush tried to draw an analogy between World War II and efforts to fight terrorism, including the Iraq war - a connection Chirac rejected.
"History does not repeat itself," he said.
In one sense, the passing of Ronald Reagan while President Bush was in Europe symbolized the decline of Western Alliance relations.
As president, Mr. Reagan was no favorite of European publics. They derided him as a "cowboy" and dangerous cold warrior.
But Reagan was of the generation of Americans who remembered what it meant to stick together in adversity. A veteran himself, he helped guide NATO through one of its greatest challenges - the deployment of Soviet SS-20 midrange nuclear missiles, and the subsequent NATO "dual-track" response of cruise and Pershing missile deployments in Europe.
Now the cold war is over. The European Union is rising in importance as forum for European identity. Those who remember the old days, such as Germany's Helmut Kohl, are fading away.
"The individuals that kept the relationship on course are retiring from politics," said Mr. Kupchan at a Council on Foreign Relations symposium last week.
Thus current Western leaders understand less about their fellows' political limits and priorities, say other experts. This can be seen in the fact that there are may now be myths on both sides of the Atlantic about the alliance and Iraq.
In Europe, the myth is that the US will be a totally different country if John Kerry is elected president, noted Robert Kagan, a Carnegie Endowment expert, at an April conference at the Brookings Institution Center on the US and Europe.
A President Kerry would undoubtedly change US foreign policy in important ways - but he would also stay the course in important ways, including on Iraq.
In the US, the myth is that is it only tried harder there would be a huge European outpouring of support for Iraq.
"I'm not sure that would be true no matter who was president on this side and how nicely we asked," said Mr. Kagan.
Different experience has given the US and Europe different points of view about many things. Americans felt the shock of Sept. 11 more strongly than did Europe, perhaps, and thus are likelier to see the fight against terrorism as a "war" than a law enforcement action.
But there are genuine cultural differences between the two sides regarding the perceived utility and legitimacy of international force, the role of international law, and other diplomatic niceties, said Council on Foreign Relations president Richard Haas in a speech in London June 1. There are truths that both sides need to realize, he said. The US, for its part, should see that there is nothing it can do better on its own, including fighting terrorism or the spread of nuclear weapons. Europe, meanwhile, should be realistic about what it, too, can accomplish in the world on its own.
"It is neither feasible nor desirable for Europe to set itself up as an independent geopolitical entity, much less as a competitor of the United States," said Mr. Haas.
The task of maintaining the trans-atlantic relationship is more difficult now that Europe is no longer the front line of the Western-Soviet standoff. It is harder to develop common ground on problems in far-off areas such as the Middle East, where the US and Europe have different perceptions and concerns.
In such cases the US and Europe may need to learn to disagree. "The best guideline," Haas said, in such circumstances is to work to isolate the disagreement."
• Ron Scherer contributed to this report.