Honestly, as a black guy, I don't have much of a problem with just following the comics. The fact of the matter is, more ethnic superheroes need to be created there in the first place, and hopefully they can grow in popularity and catch on with the mainstream. Throughout the 90's, Spawn was almost as popular as any of the flagship characters from either DC or Marvel. More creative characters need to be made like that, and this discussion wouldn't even be necessary.
One small thing I am starting to have a problem with however, is that the majority of these "American" creations, with seemingly American values, are increasingly being portrayed by Brits. The Big 3 superheroes are all being portrayed by Brits. Not to be hypocritical, even if it comes across that way, but until more Americans are allowed to portray James Bond, I don't see why we can't find someone right here to play our heroes...