Well I think its a supply thing. Europe was healthy in some, unhealty in other region before christmas, means there was a "stockpile" in shops, leading Nintendo to ship more in the US. Right know, Europe is getting their Wii's back, meaning Europe seems to get in Jan, what it missed in Dec.
Join up to the VGC Mario Kart Wii GP European League!
Or the VGC Mario Kart Wii GP Australian League!
Or the VGC Mario Kart Wii GP American League!
Or the VGC Halo 3 American League!
Or the VGC Call Of Duty PS3 League!