A big chunk of the USA was pro-German. The Germans are a huge ethnic population in the US and the British have been reviled in their classrooms since 1777. Also the Nuremburg racial laws were awfully close to Jim Crow and a whole lot of Americans were (and are) sympathetic to Nazism's basic tenets.The US was profiting from supplying both sides. The American people didn't want to be involved but the military/industrial complex did, so they saw the Japanese were going to attack Pearl Harbour and they let them. One of the few false flag operations that the US didn't plan themselves.
The question wasn't when the USA was going to enter the war, it was "on which side"?
The flaming idiots in Berlin and Tokyo changed to course of history with their stupidity but the "great anti-fascist crusade" that the Americans believe they embarked upon is an historic re-write after the fact.