It almost seems as if the dust that has been thrown up by the trans-Atlantic fracas over the U.S. action against Qaddafi's Libya is settling. The Reagan administration has found words of some appreciation for the modest measures taken recently by European governments against Libya, and the Tokyo summit will pass a resolution which pretends that, on this issue at least, the West once again stands united.

But the reality is very different. The steel wires that tie the United States and Europe together are showing signs of metal fatigue. And, even more worrying, these signs are registered with unprecedented complacency, and even a bloody mindset, on both sides of the Atlantic. Contrary to much trans-Atlantic folklore, the recent strains have not been caused by the Soviet Union. Although there can be no doubt that Moscow would prefer to deal with a divided West, Soviet policy has been remarkably unsuccessful in obtaining this objective. The most painful divisions between Europe and America have usually been caused not by Soviet scheming, but by intra-Western irritation and impatience.

Significantly, the friction among friends has been least pronounced over issues that are at the center off the NATO commitment, namely, security against the Soviet Union. True, there have been many differences of view between Washington and other alliance capitals over how best to deal with Moscow, how to interpret Soviet motives and policies and how to react to them. But in the almost four decades of its existence, NATO has gradually but surely developed a common framework for coping with this task which is so central to its existence. In the great Euro-missile debates of only three years ago, when millions of people demonstrated in the streets of Europe, and when the Soviets orchestrated an unprecedented campaign of appeal and admonition, the governments of the alliance, in the end, stood together. And European worries over President Reagan's erstwhile rhetoric forays toward the East have given way to a good deal of confidence that, while the United States may not have a constructive policy on East-West relations, it will at least not behave destructively either. The common concern over common security is still sufficiently strong on both sides of the Atlantic to make for enduring consensus on these issues.

But the same cannot be said for those challenges that are secondary to the security of the alliance and its members, namely those emanating from Third World regions. In the history of the Western alliance, these have proven the most divisive. In 1956 British and French action in Suez pitted the United States against her closest wartime allies. The Vietnam conflict stirred anti-Americanism in Europe. U.S. policy toward Central America remains controversial to this day. And now again it is another secondary threat, that of international terrorism, which has mobilized public opinion on both sides of the Atlantic against each other and has produced between the political establishments in Europe and the United States, a crisis of confidence, which could well undermine the cohesion of the alliance and with it its ability to look after its primary security task.

This is surprising only at first glance. After all, if the 16 independent nations of NATO agree on their major security problem, it does not follow that they also have to agree on the less central ones. Moreover, precisely because such issues as Suez, Vietnam, Nicaragua and Libya were and are not central to the security of any of the alliance members, they lend themselves to ideological self-righteousness. Political principles , after all, can be upheld more rigorously when to do so is not a matter of life and death.

However, what makes dissent over how to deal with Third World contingencies often so bitter is that they expose both American strength and European weakness simultaneously: the ablility of the United States to take direct military action contrasts with the inability of European governments to formulate a constructive response of their own. On most of these occasions, as in the recent crisis over Libya, the main common denominator of European politics has been to criticize the United States. It is true that European criticism has often been justified: after all, it seems scarcely appropriate that the leading power of the democratic world combats international terrorism by military counterterror. But the credibility of Europe's objections has all too often been undermined by the fact that these have served as a convenient cover for European unwillingness or inability to do anything about the problems themselves. So when America sends fighter planes to bomb Qaddafi, the disapproval of her allies is rendered that more bitter because they feel exposed in their impotence.

For this reason, high-sounding resolutions from the Tokyo summit will not stop the trans-Atlantic rot. A subtler exercise of leadership than the present American administration seems capable of, would, of course, help to reduce the friction. But even that wouldn't make it disappear. The challenge is, above all, to the Europeans themselves. They must get their act together, not by cowtowing to the United States, but by acting as if they, too, are responsible for the political credibility of the West. If they fail, then the gangrene of trans-Atlantic discontent will spread. And the Europeans who are so well-practiced at blaming America will largely have themselves to blame for the erosion of an alliance that has ensured the security of the West -- and that means Europe and America -- for so long.