Not recommended.
1) Because Greece decided it's a good idea to declare war on my puppet Turkey.
They joined allies and called them all in.
2) Then my puppet Romania refused to give up Northern Transylvania and Hungary declared war on them, calling the whole Axis.
3) Hitler ofc did not forget to also attack any available neutral state around there, adding them all to the Allies as well.
4) For some reason half of fascist/democratic american states also joined the allies later
Wow- that's a crazy outcome. Did all this happen with historical focuses on?
I'm guessing they were off since you mentioned the fascist USA, but that is still quite a snowballing of what seemed to be a mostly innocent opening move.