Martlet that isn't quite true:
The US got it's arse kicked in the pacific until Midway and the UBoat war in the Atlantic went badly for the allies until 1943.
I'm not saying that the US wasn't the major player (particularly in terms of arms and global presence, if not number of troops). I am saying that victory in WWII was achived by the Allies, and considering how slim some of the margins were (for example at the Normandy beachhead) every ally was vital.
The US did not and could not win the War by itself, neither could any of the others either. The tendancy of a small minority of Americans to consider everone else as a bit player, if at all, is not only wrong but highly offensive (I am tempted to think deliberately so by some people on this board ). Some countries fought longer against greater odds, scarificing more lives, wealth and materiel in terms of the size of thier populations (and came out of the War in a much worse state becuase of it).