Common law is important because it means than nobody, not even the President, is above the law. When the U.S. won the Revolutionary War, the Founding Fathers didn't want another tyrant to rule and not follow the laws.
It was primarily young men, especially European immigrants, who formed a large part of the workforce in Union factories during the Civil War, since most of the older men were drafted into being soldiers in the war.
1. The rise of Hitler do to the German's hatred for the treaty.
2. World War 2 would have eventually happened (even without Hitler)
3. Creating the Weimar Republic which made the great depression even worse for Germany.
