I had a professor from England say to us in class "Americans have no culture."
I need to agree that your professor was quite likely cognitively lacking. Of course, it is possible that he or she was simply frustrated over the influx of crass American mass-media culture: TV, advertising, pop music, comic books, and Hollywood films (but a good deal withing that realm is quite good). If he were a professor worthy of his degree he should have been more than aware of the wealth of "high culture" contributed by Americans: Mark Twain, Emily Dickinson, Henry James, Walt Whitman, Herman Melville, Edgar Allan Poe, T.S. Eliot, William Faulkner, Hart Crane, Ezra Pound, Cormac McCarthy, James Whistler, Edward Hopper, John Singer Sargent, Winslow Homer, Andrew Wyeth, Willem DeKooning, Robert Motherwell, Andy Warhol, Jasper Johns, Joseph Cornell, George Tooker, Jacob Lawrence, Phillip Guston, Robert Rauschenberg, Lee Bontecou, Ansel Adams, Edward Weston, Edward Steichen, Imogen Cunningham... to say nothing of American contributions to film, television, and music... including some of those working within the realm of pop music.