Europeans and Americans draw from a vast common store of culture, values and history to define sharply contrasting views on the use of power on the world stage. Only people who know each other so well can on occasion misunderstand each other so thoroughly.

This is such an occasion, as Israeli-Palestinian fighting shakes the Middle East, American military victory in Afghanistan edges toward political quagmire and Europeans shudder over U.S. discussion of dismantling Iraq’s outlaw regime. The Atlantic is suddenly a gulf of misunderstanding and dissonance rather than an ocean.

Trans-Atlantic paths diverge spectacularly in some places, subtly in others:

Israeli troops use American weapons to destroy Palestinian Authority buildings and facilities built with European Union funds. French combat pilots fly tactical air support for U.S. troops in eastern Afghanistan, but Paris says little about the missions as anti-American sentiment mounts at home and the French presidential election rages on.

Chancellor Gerhard Schroeder has shifted from emphasizing Germany’s “unlimited solidarity” immediately after Sept. 11’s terror attacks to emphasizing the limits on European support for a pre-emptive U.S. strike against Iraq. Even British Prime Minister Tony Blair has felt compelled recently to prod President Bush to engage more actively in the Middle East and to rethink the imposition of steel tariffs that undermine British companies and the Bush mantra on free trade.

Much of this Euro-American disarray is familiar; array hardly ever seems to happen in this relationship.

It is no discovery, for example, that Europe and the United States treat the greater Middle East with differing priorities, sympathies and domestic political agendas. Roughly speaking, dependence on Arab oil, guilt over colonialism and concern about large immigrant Muslim populations within their borders incline European governments to cut the Arabs more slack than do American politicians, most of whom extend unquestioning support to Israel.

But the level and quality of the present disharmony across the Atlantic is significant, and significantly different, in at least two ways. This came home to me forcefully last weekend as I listened to European visitors question U.S. officials and business leaders during the Trilateral Commission’s annual meeting here.

Despite the outpouring of deep, genuine sympathy and help from Europe in the wake of Sept. 11, many Europeans do not seem to understand the profound changes that the day of terror brought to American lives. Above all, they do not appreciate that open threats of harm and retaliation voiced by Saddam Hussein, Palestinian mobs or Iranian mullahs sound differently in the ears of Americans today than they did on the day before the attacks.

Woven into the texture of French, German and other commentary at international conferences and in domestic debate is the belief that Saddam Hussein, Islamic Jihad and the rest are the same unpleasant or murderous entities that they were on Sept. 10.

That prompts European questioning of the Bush administration’s decision to assign new and urgent priority to combating those who openly and repeatedly threaten Americans lives while working to acquire or improve weapons of mass destruction.

Europeans are accustomed to the insecurity of their geography and history. A decade after the Cold War ended, they feel more secure from the direct threat of war and annihilation than they have in centuries. At the same moment, Americans have had the security blanket of oceans and distance yanked away in particularly brutal fashion.

This alone is sufficient cause for new disconnect in the Atlantic community. But there is more: America’s absorption with homeland security and global terrorism occurs at a time of sweeping European redefinition and reconstruction. The European Union’s 15 members are working out how not if they will incorporate 10 new members in the next two to four years, while NATO is set to extend into the Baltics and the Balkans this autumn with little public debate on either side of the Atlantic (or, oddly enough, in Moscow).

In Brussels, a convention of European sages will gather twice a week over the next year to lay out some form of continental constitutional order. Blair hopes that process of clearly defining national and European-wide rights will move Britain into adopting the euro as its currency.

American minds are understandably elsewhere. But American absence from or neglect of these wide-ranging processes of institutional change for Europe benefits no one. Neither does European failure to recognize fully the dangerous new world that Americans now inhabit.

In the Cold War, Americans and Europeans actively needed each other. They quarreled knowing that the limits of discord would soon have them working together again. Now the limits of accord dominate this vital relationship. New balances of understanding and mutual help must be developed. They will not develop themselves.

Jim Hoagland is a columnist for Washington Post Writers Group.