Chile is an unhappy country, and it is unfortunate, too, because nobody notices it. South Africa is also unhappy but fortunate in that its woes do not go unremarked.

The crimes of apartheid have come vividly to the world's attention. Meanwhile Chile's Gen. Augusto Pinochet continues to jail, torture and cut his countrymen's throats.

Writer Nicholas Lemann explains our obsession with South Africa: "Apartheid resonates in the U.S. because of our own long, sad history regarding race."

Chile should resonate here, too, because of our "long, sad history" in propping up anticommunist police states because they are anticommunist and because of our complicity in bringing about the present appalling state of affairs in Chile. Frank Church's Senate committee copiously documented the machinations of President Richard M. Nixon and Secretary of State Henry A. Kissinger, whose displeasure at the election of Marxist Salvador Allende as president led to the infamous policy of "destabilization" and conditions for the Pinochet coup.

President Reagan's policy of "constructive engagement" toward South Africa has been discredited, condemned by members of his party and rejected by the American people.

Reagan applies constructive engagement toward Chile, although he does not call it that. He does not have to call it anything, since his Chilean policy is never challenged, except by a few small, hardy organizations that soldier on, gathering information about torture, disappearances, kidnaping and worse for an apathetic press, public and Congress.

Poor Chile. It needs a Randall Robinson, the head of TransAfrica, the activist group that made South Africa's plight visible to the country. Chile needs picket lines around its embassy, celebrities willing to be arrested by appointment, headlines, television coverage.

The State Department is hardly ever called upon to defend the policy toward Chile. Many Reagan officials regularly slam Nicaragua for its human-rights and civil-rights offenses. But on Pinochet, who has introduced "scientific torture," they are mum.

When anyone from Foggy Bottom does speak, it is to brag about restoring relations with Chile, which President Jimmy Carter properly broke off to protest Chile's hideous human-rights abuses. The Reagan administration says it is "supporting a democratic transition."

The Reagan administration has voted for Chile in the Export-Import Bank, in the United Nations and the Inter-American bank, invited it to rejoin naval maneuvers and, except for an occasional bleat about the state of emergency -- which Pinochet recently suspended, has given the kind of encouragement and approval extended to Pretoria by Reagan until the country called him on it.

A new coalition of all opposition parties, which is supported by the Catholic Church and excludes the communists, issued an accord listing the steps to be taken for a genuine transition to democracy. It demanded the dismantling of the murderous security system that keeps Pinochet in power.

Pinochet's crushing response was given in his anniversary speech: "Their anxiety for reaching power at any price makes them try to destabilize the government"; and "some of those who signed this are responsible for the strategy designed to make Chile a mere satellite of the Soviet Union."

The State Department had "no comment." Nor did anyone else. The contrast with the uproar over President Pieter W. Botha's defiantly negative declaration about ending apartheid is instructive.

Jonathan Fine of Boston, head of the American Committee for Human Rights, led a 10-day mission on torture in Chile in July. A member of his team interviewed a political prisoner, who reports that on his refusal, under torture, to confess to subversive acts, his wife and 18-month-old daughter were brought into his cell and tortured.

The Boston Globe reported Fine's account of the atrocity. No outcry followed.

Reagan long ago made the invaluable discovery about how few things Americans really care about.

Thanks to Randall Robinson, he found out that they cared about South Africa. The picketers prodded Congress, public opinion followed and Reagan turned around, finally, and imposed sanctions.

Such things happen when attention is paid.