AMID our introspection over the 50th anniversary of the attack on Pearl Harbor we are giving scant acknowledgment to Japan's present-day helpfulness across a broad range of diplomatic and strategic issues. "Helpful?" Is that the right word for our principle competitor?Yes. Mesmerized by frequent trade war rhetoric or, worse, by visions of a 21st century military collision between Japan and America (as in George Friedman and Meredith LeBard's "The Coming War With Japan") Americans fail to see the many ways that Tokyo nurtures trends which work to our common advantage. After years in Asia writing economic and political journalism I find myself asking this question: In a century replete with grandiose disasters, why does Japan's generally beneficial world role in the current era escape notice? Why do we equate success for them, with menace for us? In a new study on Japan's changing political role, Eiichi Katahara describes a "fear that Japan may use its financial and technological power to build a Japanese-designed, Japanese-controlled, industrial structure within the (Asia-Pacific) region - a modern version of Japan's Greater East Asia Co-prosperity Sphere." It is mostly an American fear. The truth is that the Japanese, having now displaced Europeans or North Americans as the leading investors in nearly all Asian countries, cause remarkably little resentment and less alarm in the host countries. Their profile remains low, unencumbered by the arrogance characteristic of Asia's earlier economic dominance by non-Asian powers. Even when politics takes a nasty turn, as when Indonesia and Japan differed sharply in the late 1980s over prices for aluminum and oil, Japan's disputes only rarely reach the public arena. Contrast this to our well-trumpeted diplomacy and lack of negotiating cohesion. Awkwardly for us, Japan's strength results from a trading system which we largely created and have strived to defend. And Japanese predominance in East and Southeast Asia rests, as we in more sober moments realize, on exploiting opportunities which were just as much available to us had we been less distracted by security concerns or less content with cultivating our own domestic market. To be sure, the Japanese are not "GATT-pure." But then again, neither are we, neither is any country. What Japan has done is simply to save, invest, plan, and do the necessary homework. OUR chronic misunderstanding goes well beyond this. We fail to grasp how Tokyo's influence in Asia and beyond often has a positive and complementary dimension, one that reinforces our own aims and ambitions. Unless this is grasped, success necessarily mutates to menace. Although the Gulf war is now seen as belatedly energizing Japanese foreign policy, former Prime Minister Toshiki Kaifu's government twisted the arms of Southeast Asian leaders to ensure retention of the US's security presence in the Philippines. Accepting an American agenda, Japan has also financed the bulk of an aid program for Manila. From Katmandu to Rangoon, and from Colombo to Beijing, Japanese diplomats in recent years have also moved, out of the limelight, to restrain autocratic rulers from dropping their dismal standards still further. I have witnessed at first hand how Tokyo's aid conditionality has influenced events in Nepal and Sri Lanka. In Nepal the pressure helped convince King Birendra to submit to democratic elections; in Sri Lanka, Japan's stance (coupled to pressure from the British and other Western countries) has hel ped to improve international monitoring of the terrible civil war in that country. Because Japanese diplomacy depends on quiet, face-saving pressure, it receives little attention. In Beijing, for example, the Chinese leadership knows that the size of future yen credits depends, in part, on restraint in Chinese arms exports. And China reacts as much to Japanese as to US pressure when it yields to demands for its accession to the nuclear nonproliferation treaty. The Japanese also count in current moves to encourage Beijing to help rein in North Korea's nuclear weapons ambitions. Japan's hand is visible in most of the gains squeezed from China - accession to the Montreal Protocol on Greenhouse Gas Emissions or winning visas for human rights monitors. In visits to India and other South Asian nations last year, Kaifu pulled few punches, telling his surprised hosts that the region's mindless defense spending and bureaucratic economies were doing them little good. This mirrors the message we are giving, ourselves, to reluctant listeners. Lastly, I do not deny the stupid intransigence of entrenched interests in Japan nor the damaging effect on our relationship of the old, self-aggrandizing habits formed in the bureaucracy and businesses during earlier stages of Japan's export drive. Nor am I happy about Japanese companies' behavior toward the natural environment in Asia (the tropical timber trade is a scandal). Yet for all these shortcomings, I sense a troubling lack of understanding in the United States about the maturity and generally b enign face of Japan as it meets the rest of the world. Outside the State Department, few know about this changing - and supportive - Japan. More of us should.