Couples Retreat released Oct 2009. The movie poster for the UK cut the folks who weren't sparkly white. (To see, bottom of page: http://thesocietypages.org/socimages/2009/09/02/doctoring-diversity-race-and-photoshop/ )

With Airbenders, and all the talk of race, I didn't see one mention that the lead being white was likely a financial decision (my guess on the matter).

If your audience (and this assumes you want to work with a studio that distributes globally) is potentially 2/3 from rest of world, yes you need to think about them. I'm just not sure what to think about them.

I do know when I dig into a movie these days I check out what countries it did well in (love boxofficemojo) to learn the whole story. Can't wait to see how Salt does across the world.

Tip #360 from Screenwriting Tips... You Hack: "Most people outside the USA don’t give a crap about baseball. The international market is 70% of box office. So think hard before you write that baseball spec."

I think that's it in a nutshell: avoid cultural specificity. (And if story is culturally specific, stay low budget so one market can provide sufficient box office.)