Could go either way.
USA is more experienced and has an arguably better roster, but they've failed as favourites before (2006) and they've been pretty underwhelming this tournament as well. Yeah they're undefeated, but they needed OT to beat Finland and just got by Switzerland 2-1 (though the Swiss shouldn't be underestimated, they even gave Canada a bit of a hard time, or at least Conz did). The other opponents in their pool were weak.
Canada on the other hand hasn't been overly impressive either..they had some pretty big wins against Russia and Czech but they played poorly against Sweden and deserved to lose that game. Today they played more like a team and played better overall, however I am not convinced with this goaltending.
Roy as we know has been terrible, and Visentin hasn't exactly been lights out but we haven't seen him against an overly tough opponent yet so we don't really know what to expect from him.