JAPAN HAS offered a helping hand to the nation's governors, who are meeting in Washington this week to discuss what the Reagan administration's new federalism has in store for them. The help is to come in the form of $10 billion in low-interest loans from Japanese business to finance public works and economic development projects proposed by individual states.

Heaven knows, the governors need help. All over the country, roads and highways are in disrepair, bridges and public buildings are crumbling, and mass transit, sewer and water systems are in poor shape. With most state treasuries depleted and voter resistance to tax increases still strong, the governors face new burdens from last year's cuts in federal aid and the prospect of much larger cuts to come.

>Still, it is hard to place the United States--with its high per-capita income--in the category of an LDC or "lesser-developed country"--the polite term for nations normally deemed worthy of foreign aid. What is needed is a new concept: the "ODC" or "over-developed" country. These are nations in which the majority of citizens have become so involved in their own personal prosperity that they have lost the will to devote their energies and resources to the commonweal. In such situations, it may be necessary for other countries, in which the desire for general advancement is still strong, to supply the needed stimulus for ODC public investment.

>We hope that the Japanese won't stop at the provision of basic economic assistance. There are many other areas in which they could help--improving business management and worker morale, for example, or perhaps a lesson in how to build a durable, fuel-efficient tank.