IMO, If Hitler had made an amphibious landing on England rather than attacking the USSR, Europe would have been Nazi dominated for some years or decades.

Once the Nazis had England (Scotland and Wales) they could have taken the Azores and Canary Islands. From that position, the Nazis would have controlled the North Sea and a good portion of the North Atlantic. The US would have had a very difficult time retaking Europe from the north, staging - at the closest - from Iceland.