The Communist Party USA opposed the US striking out against Nazi Germany until Hitler betrayed their beloved Stalin.
The Communists were not anti-Fascist.
This only changed (notionally, at any rate) with the Molotov-vonRibbentrop Non-Aggression Pact. Being good little obedient slaves, at that point the Communists worldwide followed Stalin's dicta to the effect that the Nazis weren't really such bad folks. This lasted, what?, two and a half years or so.
Historical note: the Left-Right dichotomy was in fact popularised by the Communists, as a means of distinguishing themselves from the Nazis, not as a means of distinguishing themselves from the assorted more democratic parties.
Socialism cannot tolerate competition; when there have been more than one socialist faction in a society, they have warred between/among themselves first, before taking on their well-known ''class enemy''. The clearest example of this (and there are hundreds) was Hitler's actions after easing von Papen out of the chancellorship in 1933. Who was Hitler's first target? Not the Jews, not the Social Democrats, not the Slavs (whom he hated at least as much as he hated Jews)...nope, it was the Communists, Reichstag fire and all.