US supplied Nazi Germany with weapons initially in the war. US sold its weapons to both sides Axis & Allied. It was making solid business and growing its economy in the solid knowledge that nobody would probably attack them. Once Japan attacked Pearl harbour - it was already late in the war - then and only then US entered the war.
Remember the march of the Nazi was halted by the British Air force & the Russian army. Thats what broke down Hitler. US just came in and waved the flag. (Even though US didnt participate in the full war - US has made the maximum war movies - dunno why!)
