When Elvis sings “American Trilogy” (a combination of “Dixie,” “The Battle Hymn of the Republic,” and “All My Trials,” a slave song), he signifies that his persona, and the culture he has made out of blues, Las Vegas, gospel music, Hollywood, schmaltz, Mississippi, and rock ’n’ roll, can contain any America you might want to conjure up. It is rather Lincolnesque; Elvis recognizes that the Civil War has never ended, and so he will perform the Union. Well, for a moment, staring at that man on the stage, you can almost believe it. For if Elvis were to bring it off—and it is easy to think that only he could—one would leave the hall with a new feeling for the country; whatever that feeling might be, one’s sense of place would be broadened, and enriched. But it is an illusion.
-- Greil Marcus, Mystery Train: Images of America in Rock 'n' Roll Music