Was entering WWII a mistake?

[Rockefeller GOP]

After the Soviet Union was attacked we could've got away with only fighting Japan, as Stalin had far more reserves, far more front-line troops etc. He still would've gotten to Berlin, and quite possibly on the same time frame if we keep supplying him with tanks, planes etc. (And keep in mind Operation Barbarossa was about 5 and a half months before the bombing of Pearl Harbor).

That said it was politically expedient to declare war against Hitler as well (Britain was an ally, and they couldn't liberate the Western Front-which Stalin wanted, alone.)

Hitler declared war on us first.

It's also worth noting we could declare War on Hitler, and still let Stalin do all the work (which is pretty much what happened anyway)

Uh, hardly...