Well, I don't know if the size of the program has anything to do with it... what happens if you try and purchase music outside the US? Are you presented with a dialog that says you can't? Does the music store even show up?
Different IP ranges are assigned to different parts of the world, and I'd bet that's how Apple is keeping out the rest of the world: simply blocking IP ranges... although I don't know much about how that works. Once the legal maze is navigated, Apple should just have to open those IP ranges for the countries involved and voila! Instant access to the store...
...and stony silence isn't a bad thing -- remember before the release of the iTMS? The rumor mills were cranking out stories of how Apple was going to PURCHASE record companies in their entirety, which was baloney -- and then they hit us with the iTMS, which is beautiful. Now, if Apple had made the information public that they were talking business with all these record companies, MANY other companies would have known and had the chance to negotiate better deals with the record companies, effectively screwing Apple's negotiations. Apple employs stony silence in order to stay ahead of innovation and other companies. It's almost a requirement to be as good as they are -- keep what they've got in store under tight wraps so no one else has the chance to see it and to give Apple the chance to make it the best.