When did German failure become virtually certain in WW2?

[compson]

No later than Pearl Harbor, that's for sure (I take it for granted U.S. would've declared war on Germany even if Germany had not done so first). Quite simply, by 1943 U.S. armaments production was outpacing every other country in the war (Axis and Allied) combined. With all due respect to the Greatest Generation, it was an unlosable war.

The question is when did U.S. involvement become inevitable, which is a question of domestic politics chiefly but also contingent on Germany military strategy. I'm not sure if Roosevelt could've finagled us into the war without Pearl Harbor, although Admiral Raeder was chomping at the bit to begin submarine warfare against the U.S. all throughout 1941.

If the U.S. doesn't enter the war, do they still sustain arms supplies to the extent needed by the UK (and more importantly) the Soviets? If so, the Soviets reclaim their losses and the UK achieves a favorable settlement.

Without lend lease, I would say Germany would've been favored to force the Soviets into capitulation (Brest-Litovsk on steroids), along with an ignominious peace for the UK.