The North American version isn’t a straight localization. Square Enix is enhancing it with more multiplayer options, an extra boss fight, and more multiplayer modes. An interview snippet also mentioned rebalancing the game by nerfing Megalfare and powering up bosses, but those changes are still unconfirmed.
Source: Kingdom Hearts: Birth By Sleep Awakens In North America With Extra Content // Siliconera

Sounds like a good thing for those who have someone to play against/with. I'm kind of lacking in that department though. Ah well.