Copland America's best composer?

Robert Gable has a new post on Aaron Copland at his aworks blog which mainly interests me because it refers back to his earlier post proclaiming Copland as "America's greatest composer."

I want to stew about that a little while. But my first reaction -- other than immense relief he didn't say "Charles Ives" -- is that it's a logical suggestion. Gable said some folks mention Duke Ellington, surely the best jazz composer; I'm rather partial to Gershwin. (I love Stravinsky, but can we really claim him?) Copland's "Third Symphony" is one of my favorite pieces of music, and I also really like the clarinet concerto.