In the ten years since the last Marine was plucked from the roof of the besieged U. S. Embassy in Saigon, "Vietnam" has come to stand for a good deal more than America's first military defeat.

Disparaging television has long been a favorite national pastime - second in popularity only to watching it.

In the American religion there stands no icon more sacred than the "free market," embodying as it does the belief that Americans must trust in the benevolence of unseen forces to fulfill their destiny of wealth and power. In times of economic unrest, however, when factories close down, workers lose their jobs, and towns become impoverished, the prayers to the mysterious market gods give way to cries of anger and disbelief.

When General Westmoreland hauled CBS into court for libel last year, the American press responded with a flood of sober commentary on a cherished subject - itself.

When in 1947 the UN handed down the Solomonic judgment that to resolve the "Palestine problem" the Holy Land would be divided into two nations bound together in "economic union," the laughter on Sinai must have been loud indeed.

When no less sacred a national symbol than Miss America found herself displayed in a pornographic magazine last summer, the public was duly outraged - at the pornographers, for profiting from a young woman's inexperience; at the pageant committee, for demanding she relinquish her crown; and finally at Miss America herself, for not knowing better.

When Yasir Arafat spoke at the United Nations some years ago with a gun in his belt, he was giving a performance in what has become the terrorist theater.

Almost from the moment the first "contra" was issued his American, made combat boots, the Reagan Administration's secret war against Nicaragua has been embroiled in a vociferous if somewhat bizarre public debate: Congressmen proclaim their outrage, editorialists confess their misgivings, while officials in Washington - who are running the war - blandly "decline to comment on intelligence matters."

"The United States themselves are essentially the greatest poem." Thus Walt Whitman, in his 1855 preface to Leaves of Grass, expressed what has been the American poet's struggle from the beginning-to wrest from the land a separate work of art.