It wasn't, in the end, a fair fight.
As a friend of mine who served in the German homeguard said (he was 15 and in a hole facing off against American troops), "for every rifle we had the Americans had an artillery piece ~ truly not the best artillery piece ever built, but they had more of them we could have ever imagined".
We did the same thing on the Eastern front, only there you had Russians doing the fighting ~ still our stuff ~ some to their designs, some to ours, but still a lot more stuff than the Germans could begin to produce under the best possible conditions.
Many historians believe that the Soviets would have crushed Germany even without a Western Front in the picture. The Russians were incredibly tenacious, they suffered millions of casualties, yet continued to move forward. Hitler's gravest mistake was to attack Russia. The German Army wasn't even fully mechanized when Barbarossa began. Neither was the Soviet Union. But their Homeland was being invaded. It gave millions the incentive they needed to repel the Germans, at all costs. Even without our help. I believe the Russian's, underestimated by Hitler, would have eventually prevailed.