Exactly Kzin, that was what I wanted to write too. It really seems like Nintendo doesn't want to release an online game worldwide at the same time. It would have been no problem to release Strikers in NA at the same time as in Europe (while SPM is probably delayed that much because of the translation). Mario Kart was under development for quite a while probably and they thought that it'd be good to have something for the holiday season in Europe too.
btw, I would be very happy about this because I really prefer MK!







