Yes this includes Western countriesA rejoice for vocaloid fans owning a region-locked 3DS as they can finally play chibi versions of Crypton Vocaloids (and GUMI). It's gonna be based off Mirai 2 btw, which is good because it has all the songs from Mirai 1 as well.
From what I've played, I like it better than Project Diva in terms of more variety in notes, but the big downside is that since it's aimed more towards the casual base and younger audience, there is a lack of Extreme mode, so expert rhythm gamers may find it a bit lacking in the difficulty department. It's still fun. (and, and all songs are full versions too, not cut to 3 minutes if that really mattered to you)