[tmgrhm]

I believe the reason is because they plan to roll out localised versions to different countries.

Although they surely won't roll out special versions to each national app store, so you do have a point there…

I'm not sure why they did it, but it's their prerogative.

Ferner, I don't think you should forget that there is still a lot of web content which is restricted by country — YouTube being a much-despised example of that, although they have obvious reasons there; BBC iPlayer being another example with similar (but far more justifiable) reasons. From those examples, I think one can guess that one of the issues may be copyright: It's easier for them to handle the copyright of just the US.