I just did a little bit of digging and FFXIII didn't sell that much better in NA compared to Japan. 1.87mil sales compared to the 1.57mil in NA. But then you could chalk that up to people around the world just not liking FFXIII. xD

EDIT: That was just PS3 sales! Including the Xbox sales kicks FFXIII up a bit in NA...

2.7mil in NA, and 1.88mil in Japan.

(Source of figures here http://www.vgchartz.com/)