Before Chancellor Helmut Schmidt's visit to Washington last week, German-American relations had plummeted to their lowest point in recent memory. It wasn't just a matter of clashing policies and perceptions. Suddenly, something far more ominous was at stake: the solid tradition of mutual trust, accumulated over decades, that had turned the tie between Bonn and Washington into the sturdiest foundation of the Atlantic Alliance. Anger and suspicion had trickled down into public opinion and the leading media, too.

Did Schmidt's visit help dispel the doubts? On a "philosophical" level it certainly should have. Emerging from the Oval Office, the chancellor finally acknowledged what his government had heretofore strenuously denied: Soviet responsibility for Gen. Wojciech Jaruzelski's coup. There is no reason to wax sarcastic over this startling change of tack. Better late than never.

On a more practical level, the Germans, with other Europeans, did move to close ranks with the exasperated Americans. They vowed not to undercut U.S. sanctions, and promised possible sanctions of their own. The vagueness of that commitment should not obscure the key difference from the response to Afghanistan. Two years ago, many Europeans (and others) rushed off to Moscow to fill the orders embargoed by Jimmy Carter.

Given the pressing need for damage limitation, Seved chmidt performed better than the pundits had predicted. And so did Ronald Reagan, whom many Germans still like to shrug off as an aging actor of B picture fame. In focusing on their agreements, the two occupied the high ground, which was in danger of being swamped by indignation in both countries.

It was high time, for, in the wake of the triple clash over Afghanistan, Iran and Poland since 1980, the Atlantic has become deeper and wider. Only a real-life Pollyanna could deny that interests and moods have drifted apart steadily over the past two years.

Yet neither of us can let resentment usurp the task of diplomacy. Both Americans and Germans might remember why we linked our fates in the first place: Europe, no matter how strong, cannot provide for its own security, and the United States, no matter how powerful, cannot afford to let Europe drift into the Soviet orbit. To do so just to punish European "ingrates" would be a mistake of colossal proportions.

Nor will finger-pointing do. Instead, irate Americans might realize that Reagan resorted to mere pinprick sanctions against the Soviet Union while leaving untouched those massive grain flows whose cutoff would have really hurt the Soviets. If deference to powerful domestic groups is somehow legitimate in Washington, can it be a sin in Bonn? In 1980, West German exports to the Soviet Union were five times higher than those of the United States. Total Eastern trade accounts for almost half a million German jobs.

And if sanctions are the key--a dubious proposition to begin with--why spring them on the Europeans only hours before they are officially announced? This is not to flog the tired old horse of alliance consultation but to call for prudence. Given the record of sanctions, the United States might do better to harness its allies to more modest measures and make them stick rather than risk yet another embarrassing spectacle of disunity.

What about the Germans who have suddenly fallen into disrepute? History has saddled them with a divided nation. Geography will make them prime victims of any military conflagration in Europe. These irreducible facts make for caution, and rightly so. Moreover, the country is ruled by a left-liberal government that, 12 years ago, coasted to power on the vehicle of d,etente and reconciliation. For Helmut Schmidt and Willy Brandt to admit that the dream of d,etente has turned stale might be tantamount to political suicide.

And yet the Germans will have to re-examine their most cherished assumptions about the realities of postwar Europe. D,etente has brought unprecedented stability to Europe, but it did not loosen the Kremlin's heavy grip on its hapless vassals. If proof were needed, it was provided by Poland.

Now that Poland has been brought into line, the West Germans can no longer pretend that ritual incantations of d,etente will finally erode the Soviet Union's imperial paranoia. Nor can they go on pretending that it is somehow possible to be both ally and broker in a world where only the United States can ultimately guaranteee the Federal Republic's security.

This is why Schmidt traveled to Washington. The significance of that trip, even if grudgingly undertaken, should not be lost on those who, in exasperation, are ready to consign the alliance to the dustbin of history.