So, in 1893, at a meeting of the American Historical Exhibition at the World's Columbian Exhibition, Frederick Jackson Turner presented his famous "frontier thesis". Read it and weep at the redefinition of America. Unless you agree with him, in which case read it and rejoice to identify yourself with the progressives who are currently mandating health care. To each his own.
Basically Turner is reinterpreting what Columbus (the theme of the Columbian Exhibition, after all) means to America. In a nutshell, this is what he does in the piece:
He outlines something he calls the "germ theory of politics" (often propounded by the advocates of a Germanic peoples reading of America which is as mistaken as his is, but not associated only with these sorts) according to which American history is defined by its population, which carries "germs" of European tradition to America and allows them to germinate (ha!) here. He fails to consider (except in a slight nod to Mediterranean civilization in the closing paragraph) the possibility that America might be at its core an attempt to preserve the fundamental principles of liberty recognized by Western culture since its inception (cf. the Gelasian principle as stated in 492). Rather, America is about the frontier, about man's "unprecedented" encounter with a pure "state of nature," which conveniently strips all vestiges of tradition from the immigrants.
His declaration that to be American is not to be German--the biggest support he really offers for his interpretation--is right on enough. But he extrapolates this to mean that to be an American is to have left behind all traditions of culture and religion (despite the obvious fact that these are the root of our Constitution, no less) and to adopt instead a purely economically motivated definition of liberty as our national telos. America, he claims, is about the ability, the freedom, to move West, to gain lebensraum, so to speak. It is based upon a freedom of license rather than upon an attempt to discern the God-given natural rights of all men. Thus he objects to the "slavery question" being taken as the crux of American national development. After all, to focus on slavery and on America's response to it is to too strongly highlight the project of preserving our constitutional and natural liberties for Turner's taste. The poor fellow would prefer to see the Civil War utterly one-dimensionally, in terms only of a struggle for economic dominance via the Westward-moving juggernaut of the railroad (cf. the Lincoln-Douglass debates, the Kansas-Nebraska Act, for more on the influence of railroad building on northern political policy--and then note that Lincoln won). In other words, his interpretation of Columbus-as-ultimate-American is a picture of Columbus-as-rejector-of-tradition, concerned only with economic gain rather than with the spreading of a tradition rooted (despite its very human imperfections) in natural law.
Note that that's unfortunately the image of Columbus that somewhat prevails. And it's quite wrong. Columbus, whether you like him for this or not (and I don't agree with him entirely here, by any means), was rather a fanatical proponent of spreading religious tradition throughout the world, and rather too inclined to neglect science altogether in his attempts to do so. So that when the quite sufficiently-educated Spanish monks tried to convince him that his plan wouldn't work because the world was far too large for him to get all the way to China without dying for lack of supplies (of course they didn't believe in the flat earth: as my Am Civ teacher likes to point out, anyone who's even glanced at one of the old Spanish statues of the Christ child holding the orbis terrarum, the sphere of the earth, finds that myth knocked right off its feet, as if there wasn't plenty of other evidence to disprove it). Go ahead and read some of Columbus' letters and diaries, and you'll find a wealth of evidence pointing to a man so religiously dedicated to bringing about a quicker Second Coming of Christ that he wanted to devote his life to evangelizing the entire world as quickly as possibly. You won't find anything of the commonly fictionalized man of science, impatient with the close-mindedness of the greatest scientists of the late Renaissance, and devoted to discovery for the sake of discovery. Obviously, fanaticism of this sort is rather problematic, however sincere the man was, and I don't necessarily agree with his project, though I find it admirable in some respects.
Turner was defining him as the latter sort, merely by presenting this paper at the World's Columbian Exposition. Of course, the real practical question resulting from his paper is whether Americans in general are like this, not so much whether Columbus was. A definitive academic answer would require pages of exposition and proof. If you want an easier to come by response, I suggest talking to one or two of the more recently emigrated families you happen to know. Preferably if one of them happens to be Irish or Italian, in which case, they can probably remember the coming of their great-grandparents to this country with almost as intense emotion as the ancestors themselves must have felt. If you come away with a sense that "yes, I suppose that America is just all about becoming tabula rasa, liberated from any sense of familial or cultural inheritance, side with Turner. If the family retains a tendency to gripe about English wrongs or obsess about Grandma's meatballs, however...take your Turner with a grain of salt.