Mind you, the American came into WW2 late. Before that their industrialists were busy selling arms, equipment, supplies and various other raw and recycled materials, such as steel, too the sides involved. It was very lucrative for them. 
By the time they got involved in both theatres  (1941), the Germans and Japanese had already caused havoc, (China, Poland etc.) while the America reaped the profits and lift them out of the Depression. The American people didn't want any part of war at that time and it was only Pearl Harbour that changed that. 
BTW, the planes used at that tragic event were made up of a lot of material sent to Japan from America.