I think this may require several PoDs, perhaps some earlier than 1933, but here are the conditions:
- America may engage in hostilities elsewhere, but not in the European theatre.
- In terms of trade and sanctions, it will favour neither side officially,
- No Notzies. The same people are in charge of Germany and are enacting the same laws but, for whatever reason, this is seen merely as realpolitik.
- Earlier hostilities in China, with Germany seen as allies in supporting the Nationalists.
- No Molotov/Ribbentrop pact
- A Soviet-backed Popular Front in Czechoslovakia?