Yes, and then Germany (Hitler) declared war on the U.S.A.!
Things would have been a lot different if they had not declared war on the U.S.A.!
It appears the Japanese and the Germans were indifferent allies.
It sure would have been a lot harder for FDR to get us into the European war. I was just a pre-teen then but distinctly remember the WHITE HOT RAGE against Japan after Pearl Harbor. Even all of my dad's America First buddies spun on a dime and were all for war, just not with Germany, which was "The European's problem. We have our own with the Japs."
Hitler, for whatever reason, solved FDR's conundrum on Dec. 10th.