[ErrantX]

I'm not sure your second scenario is as quickly solvable as you think. The loss of the uk would have been the loss of an important strategic platform - essentially allowing a second front to squeeze Germany from when it came to attack. Also it would have given Germany pretty consolidated control of our side of the North Atlantic, supply routes would have been severely disrupted.

I think ultimatelythe war would have been won but redeploying to, say, North Afric would have taken a while.