That's a lie. Germany was steamrolling through Europe due in large part to French and British commanders having an outdated perspective of war, and Russia having depleted a large amount of their military generals via purges, which left the inexperienced officers to pick up the slack.Germany was far superior militarily than the US and the US in keeping with their cowardice didn't want to fight if victory wasn't guaranteed. So they only wanted to jump in and fight them after Russia defeated the Nazis and started pushing them back in Stalingrad.
No one would've wanted to see an American military coming at them with no other front to keep at least some of their units preoccupied. America would've won that war solely based off of having a nigh-infinite amount of resources at their disposal. Germany was already running low on oil by 1941...