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?
That's very believable.
Now, had the US entered WWII and then lost, I could see it being carved up after the war, between Japan and a kind of pro-Germany Vichy state. IIRC, Hitler claimed to want to give part of America back to the Native Americans. I don't know if that would come to fruition or not.