HMX confirmed it on the Rock Band Twitter. Obviously, non-Americans don't warrant being warned about these kind of things.
See, that's why I'm annoyed. If Harmonix had stated right from the start that it was only for Americans and even said reasons as to why the rest of the world has to wait, I'd be rather understanding (unless it was just 'We can't be arsed' or something like that). But instead they just announce that it's open for business, then slip in a comment on Twitter. I don't use Twitter, and I bet most RB players don't either, so it's hardly a sufficient announcement on our behalf. Heck, it's downright lazy.