it's not as though the series pits city vs. city or country v. country in the sense of residency/place of birth etc.
The "World" is just a consideration of the world's best "players" as opposed to nations or cities.
The recent movement of Japanese/Korean players and more of Latin America sure adds more validity to that, but still I'm sure it's not the most accurate colloboration of the best of the best, but it's pretty damn close, and that's what matters.