• Because the US and UK did nothing else during the war except lend-lease of course. The bombing of German industry, blockades of their supply lines, the Africa-campaigns, extensive intelligence operations, no all of that definitely did nothing and didn’t contribute to the war effort at all.

    It’s likely the Allies would have won the war without the US involved, though it’s estimated it would have taken much longer. Without UK involvement, it’s more probable that the Germans could have achieved a victory, though perhaps not a total capitulation of the Soviets. Without a western front to guard as heavily, they would probably have taken Moscow by the end of 41 (irl they were 20 miles out). Japan would also have a much freeer reign in the pacific theatre.