Grenada invasion is a 'watershed' for NATO allies

''Young Germans come to me and say, 'You see?! You see?!' '' relates an American engaged in improving American-German relations and in countering the impression among German intellectuals that the United States is trigger-happy. He adds, ''What can I say?''

Grenada is a ''watershed,'' a veteran European diplomat comments. Both men were assessing the impact of the US invasion of Grenada. Both were worried.

In the key country of West Germany - unlike in Britain - the opponents of the forthcoming deployment of new American missiles have not yet gotten into high gear on the Grenada issue. But the West German government is bracing for a blast and has already clearly dissociated itself from the US action. (So conspicuous is the dissociation, in fact, that right-wing Franz Josef Strauss has felt compelled to take center-right Chancellor Helmut Kohl to task for not supporting Bonn's American ally.)

European public aversion to the US foray accounts for the reactions of the West German government - and the veteran European diplomat. At his most pessimistic, the diplomat fears that public opinion - which now dislikes but is resigned to new NATO missile deployments - might turn against those missiles.

(On Monday, the British Parliament cleared the way for the planned deployment of cruise missiles in Britain, despite continuing demonstrations by protestors.)

Furthermore, the diplomat fears that Grenada might at this crucial moment stall the needed coalescing of the present vague Western posture toward the Soviet Union into a realistic policy.

In his more optimistic hopes for a long-term outcome of the Grenada ''watershed,'' the diplomat suggested the negative impact on European public opinion might still be repaired by some fast diplomatic and political footwork. And a common Western policy toward the Soviet Union might still be resurrected.

The diplomat's assessment is not the product of a disgruntled anti-Reaganite. It comes from a very pro-American diplomat and a hard-liner toward the Soviet Union. It reflects mainstream thinking in the conservative governments of Britain and West Germany as well as the Socialist government of France and the coalition government of Italy.

On the pessimistic side, the diplomat noted the Grenada invasion ''will certainly make it harder'' for the West German government in the Nov. 21 and 22 parliamentary missile debate. The center-right government will get the majority to proceed with deployment of NATO Pershing IIs a month later, he suggested, but the cost in public suspicion of US impulsiveness will be much higher than before Grenada.

Grenada will ''swell the (antimissile) demonstrations and strengthen those people who think President Reagan is dangerous, irresponsible, and hasty and has a military solution to everything. The Greens and peace demonstrators have been saying this all along. It will be confirmed in the wider public's mind.''

He could not predict how serious or long-lasting this impact might be, but thought it depended on how soon the US marines go home and on what sort of government is left in Grenada. He regarded Maurice Bishop, the leader murdered in the coup that preceded US intervention as the ''least bad possibility'' in Grenada. He was skeptical that any very attractive leadership could now be found.

The diplomat viewed Grenada as stunting the process of maturing he thought has just begun in Western policy toward the Soviet Union. He defined this maturing as completing the military buildup that Reagan and NATO have begun while not ostracizing Moscow.

The Reagan administration had begun to articulate such a two-track policy, the diplomat noted, and was carrying it out in arms control negotiations, if not in other contacts with the Kremlin. The British government has been in the same position - since British Prime Minister Margaret Thatcher's speech at the Conservative Party conference two weeks ago - of preaching if not yet practicing contact as well as firmness in Soviet relations. The same goes for the French government. And the West German government is already practicing as well as preaching this line.

At this point Canadian Prime Minister Pierre Trudeau has been trying to accelerate the process of building a consensus by publicly urging an end to the widening gap between military strategy and a rational political way of handling East-West relations. ''In chemical terms, he is catalyzing an agreement which was happening anyway,'' observed the diplomat.

Grenada has diverted the Western alliance from this process by raising an extraneous bone of US-European contention.

''But at least in Bonn and London you have governments which want to minimize the difference with Washington. . . . They will say, can we actually afford to be talking East-West relations with the Reagan administration when it is (seen by European public opinion as) behaving so irresponsibly in Grenada? But they will say to themselves, we can present it domestically as taming (a solely military-minded) Reagan. . . . Basically, if people could believe Reagan is being tamed, it could be paradoxically that Grenada provides a bond'' for going ahead in developing a coherent Western policy toward Moscow.

''But,'' the diplomat concluded, ''that's all from the European end of the telescope.''