The key fact about US involvement is that most of it did not arrive until the Axis had been driven far back from its initial takings. Actually occupying territ

The key fact about US involvement is that most of it did not arrive until the Axis had been driven far back from its initial takings. Actually occupying territory was crucial, and as the Germans were driven back, transportation to the front got harder even as the Germans' transport task shrank. A great waste in the war was ineffective strategic ("Norden") bombing, using up untold bombers, crews, and ordinance. Another was expending skilled ex-pat pilots on direct combat while rotating experienced own pilots back to training.