The pressures of fast-paced global capitalism, plus long-standing cultural differences, are driving the US and Europe apart as never before.
Recent flashpoints in the transatlantic relationship have ranged from European banana tariffs to the acquittal of an American pilot charged with killing 20 tourists in Italy after his aircraft severed their ski-lift cable.
Ahead lie probable disputes over beef trade, Kosovo, and the direction of NATO.
None of this means that arguably the most successful international partnership in history is about to dissolve. The common heritage is too strong for that.
But a Europe newly unified by a common currency is becoming more assertive and more willing to criticize what some Europeans see as America's increasing tendency to act unilaterally on important issues.
"There are clearly incidents that are causing very emotional reactions and language back and forth across the Atlantic that hasn't been heard in some time, in this intensity," says Helmut Sonnenfeldt, a scholar of US-European relations at the Brookings Institution in Washington.
At first glance the banana dispute is the most inexplicable of current US-European tensions. Neither the US nor Europe grows the fruit, which requires tropical climes.
In a nutshell, or perhaps in a banana skin, the disagreement is this: The US says Europe discriminates unfairly in favor of bananas produced by former European colonies, largely Caribbean islands. Tariffs lower European sales of Central American fruit produced by US--owned firms.
The World Trade Organization, a new body which is supposed to settle this kind of thing, has sided with the US on the banana question several times. Yet the European Union has simply tweaked its protective devices, and continued on.
A frustrated US is now ready to slap punitive tariffs on a range of Europe-produced products in retaliation.
Two themes lie beneath this dispute, say experts. One is globalization: Will the EU be able to continue its long-standing practice of subtle protectionism in favor of some key aspects of its economy? (The US is itself far from immune to such protectionism pressures, it must be noted.)
Banana tariffs aren't the only barrier the US is complaining about, after all. US officials have griped long and loud about new aircraft noise rules which they claim are written so as to promote the sale of European airliners and engines.
Then there's beef. The EU has banned the import of beef from cattle treated with artificial growth hormones, a common US industry practice, for a decade. The WTO has twice ruled against this practice, and set a May 13 deadline for compliance.
The second underlying theme is the future of the WTO itself. Can the world settle thorny trade questions via an international body, while competing fiercely in a variety of markets?
In many ways the WTO has already been a surprising success. For a variety of reasons - one being that guilty member nations can't veto its rulings - it has served as a more forceful international trade cop than did its predecessor, the General Agreement on Tariffs and Trade.
The US amended its gasoline standards after the WTO judged they discriminated against Venezuelan producers, for instance.
The banana dispute is the first in which a losing party has, in essence, defied its WTO verdict. "It does threaten the WTO," says John Jackson, a trade expert at Georgetown University Law Center in Washington. "I lay the blame for that pretty heavily on Europe, frankly."
BUT Jackson adds that such strains are to be expected with a relatively new way of settling what are often the most difficult of international spats. "These are the things you would expect in the early years of totally new procedures that in some ways have revolutionized the diplomacy of international economic relationships," he says.
At the same time that globalization is roiling US-Europe trade, the lack of a clearly defined external threat has caused transatlantic security ties to wobble. The mere presence of the Soviet Union caused Western leaders to emphasize the things they held in common: a dedication to freedom, democracy, and the rule of law. Its absence has allowed things that would have been small problems in the past to become large issues.
The US and Europe are going through "a long transition and accommodation to circumstances that emerged roughly 10 years ago," says Mr. Sonnenfeldt of Brookings, a former US diplomat. "There isn't a real model yet as to how you operate together and cope with differences."
The Italian cable-car verdict, for instance, has caused vituperative rhetoric to flow among allies - most of it European, toward the US.
The verdict of a US military court that a Marine pilot was not guilty of manslaughter in the downing of an Italian cable car, despite the fact that he was flying faster and lower than permitted, was not totally unexpected to those who followed the case daily. The accident had many causes - from lax squadron leadership, to poor map dissemination.
But it caused Italy to feel anew the somewhat colonial nature of its arrangement with the US, whereby troops based in Italy are subject to American, not Italian, justice. And justice, in general, is an area where there are large cultural differences between the US and Europe.
Germany's protest against Arizona's recent execution of two Germans convicted of murder highlights one rift, as many Europeans cannot understand the US reliance on a punishment they consider barbaric.