A Canadian looks at Canada and the English, at America; Imagining America, by Peter Conrad. New York: Oxford University Press. $12.95.

What exactly defines America -- what it is, is not, and should be -- has been a matter of debate at least since the first settlers sought to define their relationship with their new country. What causes a geographical coincidence to become a country? What unites an otherwise ill-matched collection of regions? These questions have been voiced in an ongoing conversation which has neither abated nor been settled in the generations since.

For the English, of course, these speculations have a special relevance. England, writes Peter Conrad, sees America as "the country which in 1776 absconded from its motherland, and which has ever since been glamed by that spurned parent as an immature, unmannerly infant. . . ."

"Imagining America" recounts what some of the offended onlookers have seen. These observers are all English writers. They range in time from the Trollopes to Auden, and in itinerary from Niagara Falls (the focus of a funny set of impressions by Dickens, wilde, and others) to the Southwest (evaluated by a later generation, that of Lawrence, Huxley, and Isherwood). They cover a lot of ground -- culture, politics, society, addictions, pleasures, table habits.

Most of them do sound spurned indeed. For the majority, coming here confirms happily their worst suspicions; for a few, being here is preferable to being there.

Mr. Conrad seems to stand somewhere in between, astonished at the boorishness of some of his fellows, but surprised that others were actually able to remain and thrive here.

This large gathering unwittingly finds itself in the same position as did most of our ancestors, and as do we, for that matter. They are diverse; they do not agree with one another very often. Their opinions are often fascinating and sometimes irritating, but in the same measure as are the Federalist Papers, some of the work of Thoreau or Twain, a lot of Sinclair Lewis's fiction, and every third page of Norman Mailer. Appropriately, their multiplicity matches ours: They are yet another group who will not quite be absorbed into a nation unsure of exactly how much it wants to absorb any of its various groups.

Here are some of their voices. With perfect indirectness Anthony Trollope declaims, "Nothing ever disappointed me less than the Falls of Niagara." Of the Mississippi his mother cooly judged that it "presents no object more interesting than mud banks, monstrous bulrushes, and now and then a huge crocodile." "The American man," Oscar Wilde pronounced, "marries early, and the American woman marries often."

"The cable cars," Rudyard Kipling snapped, "have for all practical purposes made San Francisco a dead level." Kipling continues: "The simplicity of a decimal coinage," he maintains, is "revolting to the human mind," and, with an odd anger, "The Great Lakes have no right to act like an ocean so far inland." In America, W. H. Auden notes sympathetically, "Impermanence is taken for granted." "A place," robert Louis Stevenson enigmatically observes, "does not clearly exist for the imagination till we have moved elsewhere." And Aldous Huxley writes, perhaps commenting upon all these visitors, "To travel is to discover that everyone is wrong."

"Imagining America" is a good book -- as amusing, annoying, and compelling as are the attitudes of its inhabitants and its author. It is based on the contention that, as Mr. Conrad puts it, in America one can find one's "most recondite and specialized fantasies," that "in discovering America you are discovering yourself." Interestingly, behind the contemporary sound of this unifying premise is the conviction that guided our first citizens, the infectious idea that here one might indeed achieve one's most "specialized fantasies." And thus the questions about what America is, the debate, the conversation are renewed and go on. How could it be otherwise?