America was not interested in participating but american president franklin roosevelt felt that hitlerism would be a problem to the whole world and he promised americans for new deal policy 
he realised that USA protection lay in strengthening the england 
so USA extended its support to england by lend - lease treaty 
japan did not yeild the personal appeal of roosevelt 
and so japan replied the action of USA by shower of bombs on pearl harbour of america 1941
this led america entering the world war 2 and it bombed the hiroshima and nagasaki of japan
1 3 1