It's not just American's who can't buy music from any other country. It's the same all over the world, and there are even some people who can't buy any music because they don't have a store.
Well its certainly not technical. Basically we wait on those things that call themselves lawyers to allow us to do so.
If there's a foreign piece of music you really want, downloading from gnutella/whatever or buying a cd over the net are really your only options.