Prior to Hitler’s declaration of war on the US on 11 Dec 1941, the US Navy was engaged in active warfare against U-boats on the high seas. The destroyer USS Reuben James was sunk, with a large loss of life, and the Greer was heavily damaged.
FDR’s “Arsenal of Democracy” speech, was for all intents and purposes a Declaration of War on Germany.
Before the Nazis invaded the Soviet Union, the Left’s position was to stay out of the “Capitalist War”.