The reason most GTA games have been in the U.S. is because it's one of the most diverse nations on the surface of the earth (race wise). Somewhere like Tokyo only has traces amounts of other races or ethnicities, and pretty much everyone else is Japanese.
If you've played GTA4, your bosses are from all over the place (this is why a New York style setting works so well. You have several Russian bosses, an Italian boss, several Black bosses, several Irish bosses, and even a Hispanic boss or two. And I'm only at about 60% completion.







