THE EARLY PROGRESS reported from Paris by the United States and Vietnam in their talks to normalize relations is satisfying indeed. Barely two years have passed since the wracking end of what most Americans now regard as a mistaken effort to shape the political evolution of Indochina. But there has been no substantial reason since why Washington should not accept the Communist victory and proceed in its diplomacy from there.

On the contrary, there are substantial reasons to accept the Communist regime. It is in power. Now that the North, shredding the fiction of the South's independence, has swallowed the South, the government rules over some 45 million people who make up one of the strongest countries of the region. Certainly not out of guilt or obsequiousness, but out of the same realism that dictates ties with almost every other Communist government, the United States should deal with Vietnam.

For a while after its victory, Hanoi evidently felt it could squeeze "reparations" - in effect an admission of guilt - out of the United States. When it sobered up, talks became possible. The Vietnamese are, helpfully, taking further steps to provide information on men missing in action. It is almost certain that no person considered an MIA is still alive. But the quest for more information must go on. Crude intrusions, by the way, like the gratuitous no-aid-for-Vietnam resolution passed in the House the other evening, can only complicate the process.

The Nixon-Ford administration could not rise above its humiliation on the Vietnamese ground. Jimmy Carter is unburdened by similar personal or political hangups. He has dropped American objections to United Nations membership for Vietnam and pledged an early ending of the trade embargo. Vietnam's desperate need for access to the international economy, to advance reconstruction, assures Washington leverage to see that relations are restored on fair terms.

There is no bright new day dawning in official American-Vietnamese relations, though no doubt there will be intense and diverse emotional meanings in the official passage for many individual Americans and Vietnamese. The scars are too deep for it to be otherwise. There can be, however, mature acceptance of the mutual advantage in drawing as much as possible of the poison of the past and in arranging future cooperation where it is in the interest of both to do so.