In this 17 minute clip, Robert Higgs gives details of what the USA was doing before the German declaration of war on the USA after the Japanese strike on Pearl Harbor.
Far from being a peaceful neutral country the USA was running a shoot on sight policy in the Atlantic and helping with convoys of Ships to the U.K.
In the East, the USA was, amongst other operations, engaging in economic warfare against Japan. Robert Higgs gives full details of how deeply the USA was involved in measures against Germany and Japan