The Melting Pot Is A Confounding Idea to the Japanese

LEAD: THIS time, it was not Japan's Prime Minister who made a remark offensive to blacks.

THIS time, it was not Japan's Prime Minister who made a remark offensive to blacks.

It was a man who would like to be Prime Minister.

Michio Watanabe, a leader of the Liberal Democratic Party, told a party gathering last week that American blacks have no qualms about going bankrupt.

He quickly apologized and retracted his statement, but his remarks brought a sharp rebuke from the American Embassy here and set off another swell of criticism about Japanese racial attitudes.

The episode revived memories of two years ago, when then Prime Minister Yasuhiro Nakasone said that America's black and Hispanic populations lowered the nation's ''level'' - whether intelligence or literacy was never clear.

As Mr. Watanabe's slip made clear, neither the recriminations from that remark nor Japan's expanding international presence has brought a corresponding understanding of people who are not Japanese.

Centuries of isolation on an island populated almost exclusively by one ethnic group have created an insular culture.

Unlike Americans, who have had to learn - painfully, slowly and amid social convulsions - how to accommodate different cultures, the Japanese seldom encounter anyone in their daily lives who is different from them.

With so few minority groups living in Japan, there is no one to pressure Japanese into confronting their own prejudices, or even recognizing them as such. That is why Mr. Watanabe insisted that there was no racial animus in his remark. And sometimes Japanese are simply ignorant of what is considered offensive.

They were dumbfounded by protests in the United States last week after The Washington Post reported that Little Black Sambo figures and black store mannequins with exaggerated racial features were popular in Japan. The manufacturers have started recalling the items. Threatening Differences

For the last few years, the Japanese have embraced the idea of ''internationalization'' - opening up Japanese society. So far, it remains a slogan.

''The discussion has started, but no one knows what it really means,'' said Yoshimi Ishikawa, a writer who has criticized Japanese attitudes toward foreigners.

In a society that draws so much of its identity and security from predictability and shared assumptions, any differences are threatening. And images of other racial and ethnic groups tend to form in a vacuum.

Japanese newspapers write a great deal about violence, poverty and low educational levels among poor black and Hispanic Americans, but they seldom discuss the black and Hispanic middle classes.

American movies shown here, with their shocking scenes of inner-city violence, rarely balance the portrait.

For the most part, the Japanese take these assumptions with them when they venture abroad. Last year, 518,000 Japanese were living overseas, and nearly seven million traveled abroad.

But Mr. Ishikawa, who lived in California for many years, said that few Japanese people living abroad get to know any members of ethnic minority groups.

Indeed, many of these trips reinforce racial stereotypes. Japanese tourists, who are used to carrying large wads of cash, are warned repeatedly about the dangers of American city streets, and told that the danger often has a black face. Those who do venture into black neighborhoods hear little about the strengths of black culture. Guides' Warnings

''Sometimes there are optional trips to Harlem, and the guide says, 'Don't go out alone, whatever you do,' '' Mr. Ishikawa said.

''Or if they go to L.A., the tour guide takes them to Watts and says, 'This is the place where there was a big riot, and hundreds were killed.' ''

Japanese companies in the United States have been the targets of several discrimination suits charging that they have failed to hire and promote enough blacks or women.

Last year, Japan became the world's leading trader with South Africa. Japan's Foreign Ministry has tried to pressure Japanese companies into scaling back, but the response has been so lackluster that it has been reduced to threatening to name the leading Japanese traders with South Africa.

Within Japan itself, other Asians and minority groups complain of discrimination. The 700,000 ethnic Koreans who live in Japan remain victims of discrimination in jobs, loans and housing.

Japanese also shun ''burakumin,'' descendants of tanners and butchers who were considered unclean because they worked with meat. Many companies still circulate lists of burakumin families and will not hire them.

But Mr. Ishikawa, critical as he is of Japanese attitudes, notes signs of change, particularly among young Japanese. He points to a surge of interest in Korea, fueled by Japanese respect for the nation's economic success.

Moreover, he said, the adulation of black rock stars and athletes such as Michael Jackson, Lionel Richie and Mike Tyson has given young Japanese a much more positive view of blacks.

Yet, as Mr. Ishikawa acknowledges, these images feed another racial stereotype - that blacks can succeed only as athletes or entertainers.

''I do believe we will become more open to different people,'' he said. ''But unless other countries criticize Japan, we will not wake up to this kind of problem.''