The Soviets would have taken a much longer time to clear up the remaining NAZIs and recover enough before attacking Britain. Our excellent Navy would have made it very difficult for them to cross the English channel, their Navy was rubbish in comparison.
By the time they would have been ready to invade, the USA would have had the atomic bomb. It would have been in both Britain and the USA's interests to have nuclear missile bases and nuclear bombers in the UK. Hence the Sovs would have had to leave us alone.
I'll admit that we British would have ended up speaking Russian without the USA's help. But not bloody German.
Yes, Roosevelt could be a bastard. But I think that the most important contribution we made was the sheer volume of materiel.
The Hun had better quality, but we had so much more quantity that it didn't matter.
A sad thing today, to see Britain disarmed.
Be Seeing You,
Chris