I assume for that to have happened, the most likely conditions would have been:
The UK entered into a coalition with the Axis powers.
The USA agreed to a non aggression pact. Japan didn't attack Pearl Harbour.
Russia was fought back and whilst not conquered, was in a state of cold war with Europa.
How different would the world look today?
Mathematically speaking, if the Germans had 100 active U-Boats at the start of World War 2, instead of the 30 they would have beaten the UK by starving us out. Luckily they didn't have that. Also they were plagued by torpedo issues. Then the UK would become a puppet state similar to Vichy France I imagine.
Another scary prospect is that the Nazi's had V2 rockets, an early ICBM effectively. Additionally, they were also working towards the atomic bomb themselves, if the Nazi's had that before the US did I can imagine that probably, New York City and possibly St Petersburg would be blown to smithereens. With the threat of more to come and a few more surrenders would be likely.