It’s a surprisingly grey area - until the US was dragged into the war by the Japanese, they took a largely neutral stance, in no small part due to US business interests in the third reich. The most they extended to the allies prior to that point was lend-lease - because the profits were considerable. Arming both sides was one hell of a hedge. There were, even while Europe duked it out with the Nazis, widely attended and supported Nazi rallies in venues such as Madison Square Garden. Truth is stranger than fiction, and is a nuanced beast.