I think ninenot has a definite point that high art is simply not an American tradition. It just isn't. I would add Menotti to the list of 20th century music artists, but there aren't that many.
I do think, though, that it is worth considering that music education was sorely lacking period, in the catholic schools, at any rate. I learned my vocal technique from a Jew who studied in Florence. It definitely wasn't from anything I learned in school.
Yah, and whosits who wrote "Pines of Rome"--et al.
Agreed that XXthC. America is a wasteland.
And grade/high school music? Sucked. (SSND's and Jebbies, respectively.)