And declaring war on the U.S. when he didn't have to. We were SO pist at the Japanese that I'll bet that if he had stayed out, we'd of said something like "Screw Europe, we've got our own enemy to face." and concentrated on Japan.
I read where DeGaulle was in conference with some other Free French people when an aide burst in, saying that Hitler had declared war on America. DeGaulle told the assembly, "We have won the war." and many thought he was crazy. Apparently he recognized America's industrial capacity and had a glimmer of what we would do with it.
After our violations of neutrality and eventual entrance in WWI, I’m sure Hitler knew it was a foregone conclusion that we’d be in the war.