I can understand when I play late at night but even during the day I'm still paired with mostly Japanese players. I'm in the South West of Canada. I shouldn't be paired up with that many Japanese players. The US is right there. Unless the US sales were that bad.
This is pretty much my situation a few times I've played the game. Around my time (eastern US) I usually come across tons of Japanese players. Even during the afternoon, I still keep getting them even though it's supposed to be around night over there.
I really wish there were more Americans, Europeans, or anyone else outside of Japan whenever I want to do online, but it seems to be an uncommon occurrence. I'll always go up against skilled Japanese players. -__-
As for the game's US sales, I'm not too sure how well it did. Maybe not as much as Japan's sales, but again, I don't really know.