WHAT IS IT with the socialist government of Andreas Papandreou in Greece? He is capable of the most blatant anti-Americanism and anti-Westernism; he attacks Solidarity and charges the United States with "expansionism and domination." True, he has been careful to maintain structural links with NATO, renewing American base leases and undertaking to buy aircraft that will tie Greece to American suppliers until the end of the century. Yet there is an unsettling erraticism in Greek policy under Mr. Papandreou, a hint that he might lurch far left past a point of no return.

His latest act, an internal one, ordinarily would not draw foreign attention. It is so typical and disturbing, however, that it has been widely noted. Mr. Papandreou had promised to support parliament's reelection of Constantine Karamanlis, the conservative elder statesman known for his emphasis on keeping close ties with the West. The prime minister stunned his countrymen, however, by dumping Mr. Karamanlis. The president now due to be chosen, being beholden to the left, will not easily be able to perform Mr. Karamanlis' balancing role, even if he chooses.

This is no small matter. Mr. Papandreou's PASOK movement is heavy on Marxist and Third World slogans and heavily influenced by the communists. By his overt anti-Americanism, some say, he buys political room for the pro-American strategic connection, which is vital for Greece to defend itself against its NATO partner and regional rival, Turkey, and for general reassurance in a corner of the world where Soviet power is strong. But this is an inherently unstable arrangement. A respected Greek analyst, Panayote Dimitras, writing in Foreign Policy magazine, fears that "NATO's Romania" -- a reference to the Warsaw Pact maverick -- may yet become "NATO's Yugoslavia" -- the real Yugoslavia broke with the Pact.

So the United States has reason to be concerned about Greek policy.

But the United States also has reason to be concerned about American policy. The question that too few Americans ask is how a friendly democratic country such as Greece, which fought with the United States against fascism and which the United States then helped save from communism, came to its present confusion. The key part of the answer is that Washington carelessly aggravated the fears and frustrations of Greeks of all parties by appearing too friendly to the colonels who ruled Greece in 1967-74 and to the Turks who invaded Cyprus in 1974 and hold part of it to this day.

Nobody ever said the Greeks were easy to get along with. They have, however, the leadership of their democratic choice, and they have their grievances, legitimate as well as illegitimate. The former need to be tended to, the latter dismissed.