Probably Unit33 will know the answer to this but when I'm playing Mario Kart Wii online, I can only choose worldwide, not by continent :(
When I try, it just stays at the loading screen for endlessly.
Since my internet is fast, it can handle playing with people from half way around the world but I still wouldn't mind playing with North America.
Note: I have the European version of the game but it shouldn't affect it... (or does it?)
Unfortunately I don't have a definitive answer,
it's likely that it's the Nintendo Wifi connect, it's highly
erratic, often I am unable to connect at all.
So keep attempting to go local, and your version of the game
shouldn't effect it. :panic: basically,I have no idea,
look around some Nintendo related forums, they will probably have
a more exact answer.