I'm pointing out that 'we' in 1939 means 'not the United States.' Essentially, your argument, since you invoked alternate universes, requires Americans to have an army large enough *to* invade Nazi Germany in 1939. Such a United States would have turned into a military dictatorship in the 1930s, or at least that's what actual Americans of the time believed. If you're going to invoke trite analogies, at least use semi-relevant ones like Saddam Hussein and Kuwait (never mind that the 1980s was a long lesson in how superpower backing and infinite logistics were useless in Iraqi hands).