THE rampaging and looting by Zairian troops, and talks now between oppositionists and dictator Mobutu Sese Seko on forming a government that opens the political system, are events that don't seem to involve Americans. But the United States must share responsibility for the tragedy of Zaire.More than 30 years ago, the US government helped plant the seeds of the chaos now engulfing Zaire. When the Congo became independent from Belgium in 1960, Washington was hostile to new Prime Minister Patrice Lumumba who it deemed friendly to Moscow. It supported Mr. Lumumba's opponents, who captured and killed him. A young Army colonel, Joseph Mobutu, reportedly paid by Belgian intelligence and later the Central Intelligence Agency (CIA), seized control of the Army. Five years later, after the CIA helped mercenaries put down internal rebellions, Mr. Mobutu abolished civilian government and declared himself president. The "anti-communist" Mobutu visited China, North Korea, and Romania and used them as models for his personalized rule. He set up a one-party state, ran public indoctrination sessions in "Mobutism," organized neighborhood committees to ensure conformity, and even put his picture on Zairian currency. The government took over the major industry, copper mining, and for a brief period nationalized - and looted - all foreign businesses. Mobutu enriched himself, his tribe, and the presidential guard. He built no schools or hospitals; churches carry out most social services. Nearly 2 in 10 infants die before their first birthday. The society is based on corruption by anyone with authority: underpaid school teachers demand bribes for grades, hospital guards extort money from patients seeking admission, and policemen shake down passersby. The American line has been that Mobutu had to remain for the sake of "stability and unity." State Department officials have told me that there is no alternative. "They said they would replace him, as if we were all imbeciles," said Kititwa Tumansi, a leader of the new Social Christian party. "Imbeciles because we didn't know how to kill others as he did." In 1977 and 1978, President Carter helped save Mobutu by sending logistical help for French, Belgian, and Moroccan troops to stop an invasion of exiles based in Angola. He argued that Cuba backed the exiles, which was not true. Opponents of Mobutu in 1980 organized the Democratic Union for Social Progress (UDPS), led by 13 parliamentarians who called for democratic change. They were arrested and spent most of the next decade in prison, "rusticated" in interior villages, or under house arrest. The Reagan administration ambassadors never met opposition leaders. They didn't want to annoy Mobutu who was allowing the CIA to use Kamina air base to covertly supply UNITA rebels in Angola. Then Romanian dictator Nicolae Ceausescu was executed. Mobutu's family and Mr. Ceausescu's had been friends; Mobutu even talked of him as a model. Zairians began to call for change and to speak freely in public places. Mobutu called for national consultations in January 1990 and traveled around the country asking people what they wanted. The answer: democracy. He was shocked. Secretary of State James Baker stopped in Zaire a few months later after the Namibian independence celebration in March 1990 and met with the dictator on his yacht for an hour. "The US used to tell him, 'Reform, you are making our task difficult with Congress' ," said Nguz a Karl-i-Bond, then Zaire's foreign minister. But Baker said, "Change or we can't help you." There had been help - over $1 billion in economic and military aid since 1962. Nguz told me, "It was the first time they told him there is a linkage." On April 24, Mobutu promised a multiparty system. But he had second thoughts about giving up power so easily. He sent his troops to break up UDPS rallies by firing into the crowds. In September, finally responding to opposition demands to hold a national conference to determine the country's future, he packed the meeting with his flunkies and the oppositionists refused to attend. Meanwhile, Mobutu's grand-scale theft and mismanagement brought the economy so low that at last he lacked even $10 a month to pay his troops. In return they rioted and looted whatever goods still remained in the cities. So much for stability. At a gathering of young professionals, one man told me earnestly, "Stability is not made around a man, but around democratic institutions." For Washington, however, the prime interest was having an anti-communist ally. For the people of Zaire, that was a disastrous misfortune.