I don't know which is the more dominant factor, the XBOX 360 (7 Year old console) doing really well in US and UK, or the others doing really meh in those countries.
I mean we have XBOX 360 > 3DS in both despite 3DS having 3DS XL and NSMB2. We could have X360 approaching Wii lifetime sales by the end of this year or sometime next year if things continue the way they are. Then we have it receiving a boost while the PS3 doesn't with the launch of Borderlands 2.
Then we have software. Besides Borderlands 2 (Impressive Debut), US software sales are overall terrible. Only 12 titles (including 3 versions Borderlands 2) are above 10k in the US. Of those 12, 2 are PC games. This pales in comparison to a few years ago when there were normally 20 to 30 10k+ games even when PC games weren't tracked (I think). The new gen needs to come quickly!
Also, MK Wii > MK 7! o_O