I would guess the war would have ended pretty much the same way. As 7/8 of the entire German war effort was for the Eastern front against Russia, clearly the East was the decisive battlefront anyway.
It would have made the Western contributions smaller as there is no disputing the value of the Canadian contribution. And the convoys would have been smaller and forced to travel farther distances to Europe. Still, the US industrial capacity (as well as the UK) would still have enabled the convoys, the D-day invasion, and the other events that occurred in the Western front.
What I think might have happened is that the D-day invasion would not have been ready as soon so that either it would have been delayed a couple months (perhaps ready in Aug or Sept.) or there would not have been an invasion of Italy. These would have enabled Russia to control more of Europe during the cold war; Austria, more of Germany proper, and perhaps even Italy.