THE 50th anniversary of the Japanese bombing of Pearl Harbor wouldn't be getting quite the attention it is except for the tense state of United States-Japan relations. Friction over trade, and over the suspicion that Japan is now practicing economic expansionism, gives that historical event dramatic lighting.But much of today's rhetoric about a new conflict with Japan is overheated. Without question, the two countries are locked in economic competition. And without question, Japanese tactics in some product areas - such as auto parts and video games - have tended to eliminate competitors. But the problems arising in the economic realm should lead to negotiation and mutual understanding, not talk of a new kind of "war." From the Japanese perspective, American consumers are simply opting for the better product. "Made in Japan" has become a stamp of quality. But is Japanese commercial ascendancy built on "unfair" practices? A recent edition of PBS's Frontline explored that contention; the experiences of US business people who have tried to compete with Japanese industry or share a market with it were jarring. The words of "Japan bashers," who warn that US industry is being overwhelmed by a competitor who plays by different rules, ought to be taken seriously on both sides of the Pacific. Washington has to understand the hard realities of its economic competition with Japan, and Tokyo must understand that protectionism could resurge if Japan is widely seen as an economic invader rather than a partner. Partnership has been a byword of US-Japan relations for 40 years. But the US has been the senior partner, with Japan always following. That's changing. Japan's economic vitality outstrips that of its onetime mentor and protector. Japan's role in world affairs is growing. It may let its soldiers participate in UN peacekeeping operations, a departure from its policy of never again sending troops abroad. But the changes needn't be ominous. A more activist, independent Japan can be a positive force. That, however, could depend largely on new thinking within Japan. In the whole range of its foreign relations - trade, commercial partnerships, foreign aid - Japan will have to convince world neighbors that its goals are broader than economic self-aggrandizement. Its leaders work within a political system that emphasizes consensus and can tend to discourage the emergence of new ideas. Yet such ideas will have to emerge - foremost among them the vision of a strong yet benevolent Japan.