Basically, what I'm doing is putting American troops where they wouldn't be during the time period I'm talking about (I think. Despite my research, it's hard to tell exactly where everyone was at any given moment). But, I'm going with the conceit that Captain America and the Howling Commandos existing probably changed things a little, and maybe the Americans got further into Europe earlier than they actually did, due to Steve and the boys clearing the way for them.

It's a much smaller inaccuracy than my previous one of assuming one of the countries involved was netural, when they were actually German-occupied. That's a little too big a change from history for my tastes. :-P