> It only joined the war after Europeans had already killed more than 23 million Germans, and destroyed most of its military.
German military casualties were only 5.3 million by the high estimate. Total German casualties were only 7.4 million by the high estimate - for the whole war. So... I don't know where you get your ideas, but they are objectively very wrong.
That said, the US was far from ready to advance on the German heartland until after the time they were pottering about in Africa. It was a way to look busy.
Staying out long after the split, while Germany and Russia gored one another, was clearly the wiser course. Entering before the Soviets could subdue Germany and overrun western Europe was necessary. But any claim that the US had any sort of primary role in defeating Germany remains nonsense.