Centrism implies edges (or extremes). Where is the center on the surface of a sphere? It is arbitrary or, perhaps, it is where we are at the moment. The discussion of globalization vs. localization ignores McLuhan's promised global village. The very medium we are using to discuss these issues has spontaneously generated a small community focused on a very small subject. The fact that I have no idea where the other participants in this discussion are physically located has no impact on our relationship.
The promise of the new millennium is the ability to find and connect with individuals from disperate locations and contexts. I suggest that if a composer can't find an audience, s/he just isn't trying. This in no way needs to discount the impact of locality. Kentucky bluegrass music is very popular in Japan.
American music is not monolithic. It has always been a blending and reaction to historical, cultural and personal influences. If American music is definable at all, it is in its staunch refusal to be defined.