IN THE SUMMER of 1776, Americans considered themselves to be atrociously and most unjustly burdened by taxation. That complaint always astonished the British, not to mention the other Europeans, for by their standards the Americans were very lightly taxed. None of that has greatly changed over the succeeding two centuries.

Irritation with government in general, and suspicion of its intrusions, continue to characterize the American political mind at work. The Reagan administration, the worst of it along with the best, stands firmly in the national tradition. But there has to be more than that to the idea of the United States. Resentment of Washington would not alone hold together a highly disparate population spread across a continent. It takes more than fireworks and a parade once a year.

If 1776 had been no more than a tax rebellion, it would have shortly petered out like all other tax rebellions. The revolutionary movement became a serious matter, and a real threat to British rule, at the point at which most Americans began to think that they had more in common with each other than with the places from which their families had originally come. They were not only against British taxes, they found, but they were in favor of a new kind of citizenship that they defined in the first few lines of the Declaration of Independence -- the part about inalienable rights and so forth. The idea was not only that the people were to improve the character of politics, but that this new politics was to improve the character of the people. This sense of the common enterprise has proved remarkably durable.

It is currently fashionable to argue that the country is better off to the extent that people are left to use their resources wholly to pursue their own interests, no matter how crass and self-centered. There are many organizations in Washington this summer promoting that opinion, frequently for reasons that turn out to be related to the tax legislation now before Congress and whether the top rates should be even lower than President Reagan has proposed. But from the beginning the idea of the United States has been that government is not merely a necessity but a moral commitment requiring its citizens to contribute to the country's development in many ways.

Americans know that. But they rarely think about it in relatively pleasant and serene times like the present. Adversity brings the country and its ideas closer together; you saw it happen during the episode last month of the hijacked American hostages and the murder of one of them. But the surviving hostages have been released and here at home attention is already moving to other things. The Fourth of July serves the useful annual purpose of inviting Americans to recall the purpose for which their country was founded, and to consider whether this great enterprise does not require more than assailing the tax rate and George III.