The United States and Japan are in the midst of a crisis of understanding. It is the most profound the two nations have faced since World War II.
Japan's $18 billion trade surplus with the US is the immediate cause. But the trade problem has only brought to a head frustrations and resentments that have accumulated over many years.
In Tokyo and in Washington, cherry blossoms, symbol of Japanese-American friendship, will soon open and waft their delicate fragrance through the air. Diplomats have been rushing back and forth across the Pacific alluding to this friendship and trying to massage away the irritations that hang heavy and unspringlike over the two capitals.
But the crisis will persist, say longtime Japanese and American observers, until at least two things happen:
* On the US side, a reversal of the almost universal perception that Japan is an unfair trading partner. Americans feel that Japan exports manufactured products from cars to computers in ever-increasing volume to the US, but restricts US imports through devious devices. Linked to this perception is another - that Japan spends next to nothing on defense and depends on its security treaty with the US.
* On the Japanese side, actions sufficient to reverse the US perception. The sheer size of Japan's economy and the far-reaching impact of Tokyo's economic decisions require the Japanese to show far more initiative and leadership in the global community.
Demands and grievances are pouring into Japan today, not only from the US but also from Western Europe and developing nations. The demands may be paraphrased: What have you done for the world lately?
The demands arise from a perception that Japan takes advantage of the world free trade system while shouldering only the minimum of the connected responsibilities. Also, Japan's record as an international partner shows a lack of generosity - extending from caring for refugees to development aid.
''If only, long before this trade crisis arose, we Japanese could have done something magnificent that would have made the whole world sit up and take notice,'' laments a prominent journalist.
Most Japanese, however, react to American and other foreign criticism of their country on the trade issue as grossly unfair and perhaps even racially motivated.
The Japanese perceive themselves as a small island nation bereft of natural resources, making its living for the past hundred years by importing raw materials and turning them into manufactured goods. Exports give the Japanese the wherewithal to buy more raw materials, to make more goods, and to improve their standard of living.
''We have to have a trade surplus in manufactured goods in order to make our living,'' says a high government official. This perception is widely shared by his countrymen.
The Japanese are also proud of their reputation for making high-quality goods at reasonable prices. They see themselves as working harder and demanding higher standards of craftsmanship than others. They say they shouldn't be penalized for this.
The Japanese genuinely believe their market is open to foreign goods. They say the reason foreign goods do not sell better in Japan is that foreign manufacturers do not try hard enough to meet Japanese tastes and demands.
But the US and Europe say the Japanese market is closed. They see the Japanese as an insular people whose lack of interest in leading the world community has a decades-long history. These perceptions did not begin with the generally depressed world economic climate of today.
As long as the US and Western Europe were prospering, these perceptions were a minor but persistent irritant in overall relations.
But when unemployment and inflation soars and the economy remains stubbornly depressed, then the cry that Japan refuses to play by the rules and should be penalized gains an emotional momentum whether in Detroit or Hamburg, New York or London.
It is this that lies at the heart of the current transpacific journeys. Japanese Foreign Minister Yoshio Sakurauchi has just been in Washington for talks with President Reagan, Secretary of State Alexander Haig, and leading members of Congress. US Defense Secretary Caspar Weinberger is in Tokyo March 25 to 28 to see Prime Minister Zenko Suzuki, Defense Minister Soichiro Ito, and other leaders and to address the Japanese news media. Vice-President George Bush is expected in Tokyo at the end of April. And in June, Messrs. Reagan and Suzuki will have a bilateral meeting during the seven-nation Paris summit.