Answer:
Attacking the Soviet Union, in general, was a mistake. If Hitler had invaded Britain would have ended the war in Europe and the Nazi Empire could have been a reality. The invasion of the USSR was even if Britain had been dealt with, would still end badly for Germany. The outcome of a Nazi win would be unlikely if they were to go against the USSR again. Hitler should have settled for Britain and not declare war on the USSR or USA. There are many possibilities of what could have happened but it is unlikely Hitler would get the lebensraum that he advocated for.