If Hitler would have solidified German control of an area, before adding another fighting front, he would likely have won. He overextended the German forces and their ability to resupply.
If the US stayed out of WWII, Hitler would likely have won too. Most of us were mostly German in the 1940s, many not long out of Germany at all. Hitler would have been smart to heavily court German Americans, to at least get them to not get involved.
Keith
Google the American Bund which was a German nationalist organization that was attempting just that in the US before the war, the Bund was a successor of the FONG which was started and backed by Rudolf Hess, after the FONG was declared unpatriotic by congress by the special committee of Un-American activities the BUND was established in its place which was backed by and funded by German nationalists who knew the trouble they would have if the US got involved in the war, the purpose of the Bund was to try and influence the US government and promote the Nazis and Hitler in a positive light, it also tried recruiting German Americans to its membership believing if they had enough they could turn the US from getting involved again Germany while the vast majority of German Americans rejected it, it’s still hard to know just who was involved because of the secrecy of the membership
The most well known moment was the 1939 rally at Madison square garden where 20000+ members gathered and a estimated 10000 protesters gathered outside