The Great Depression changed Germany politically by the formation of the Nazi party and the development of fascism or a complete dictatorship of the Germany's elite industrialists and they blamed the Jewish people on their economic problems thus deflecting criticism of bringing it on themselve ie the big industrialists. As for America entering the WWII, of course that was when the Japanese fascists attacked and burned Pearl Harbour thus forcing the US to respond and go to war.
It allowed many business' to expand without interruption from the Government.
