More friends having 360s in the US = more 360 sales
More friends having PS3's in EU = more EU sales
Though this is circular logic, the current state is leading to these outcomes.
The GT argument does not hold so much IMO as we have not yet had a full-game release this gen. I think 360 is better marketed in the US, I mean we hardly get to see any console or game adverts in Malta or Italy.