Answer:
The Nazis win and a weak Nazi regime would be established.
Explanation:
The Southern Embargo on cotton led Britain and France to become less reliant on American cotton. Colonies like India and Egypt decreased Britain and France's reliance on American cotton, which was a staple of the Southern economy. The South emerged economically devastated, and had a long recovery. But if they did not return to the Union, and they could not rely on Northern industry, this recovery would be even slower. And with the division, both parts of the union would be significantly weaker. For this reason, America would have played a less significant role in WWII. The result is speculative of course, but it's possible that if America decided not to enter, or could not produce a strong army, then the Nazis would have had a much easier time with their goal. I think that the only scenario where the Nazis would have won is an instance where they developed nuclear bombs first--and used a scorched Earth strategy to eliminate the Russian threat. This would be my speculation, but past victory, it's hard to say what would have happened. The Roman Government lasted for thousands of years, and perhaps the Nazi regime could last for a while before becoming de-stabilized, but I don't think it would have been a strong centralized regime. The reason I say this is because not even Caesar or Napoleon (brilliant diplomats and military strategists) could not achieve this. But this (of course) is speculative.
(Fun question, never done "hypothetical history")
