Haha, I know this isn't the point you were trying to make here, but none of these girls are American either.
Now, this is a total generalization, but I've heard that American (and to some extent, Western European) girls have a bad reputation for being entitled/whiny/having bad work ethic, which could account for their lack of representation in high fashion. Staying thin requires a ton of discipline, and walking shows doesn't pay anything... I can see why certain people would rather stick to more commercial campaigns which are less strict and pay better. By contrast, Eastern European/Siberian models are known for being harder working and complaining less (probably has to do with fewer opportunities back at home). Of course, everybody is different and your nationality doesn't preclude you from being a royal pain in the ass, so take all that with a grain of salt