Generally, releases include two basic permissions... the right to photograph, and the right to use said photographs, (along with a lot of legal yadda-yaddas). Signing the release in the country where you're shooting allows you the right to record the photograph there. Adding the term "world wide" to the portion that covers subsequent use SHOULD cover you when the photos are published elsewhere in the world.
I'm a photographer, NOT a lawyer, so my suggestion is to consult your attorney; don't rely on my advice alone. ALSO, laws differ everywhere. FAR better to be safe than sorry.