Suppose you're back in the WWII years and you just learn about German atrocities.

[HereSince1628]

16. I was hoping for something that looked rather less post hoc.

By 1945...all the rationales end up being framed around the experiences of America already being engaged in war which really creates a problem of post hoc-proctor hoc for explaining the threats that took America to war.

You argument about having modern war-fighting capability applied to the contemporary world would mean the US is threatened by scores of nations. I don't think we live under that sort of real threat.

Roosevelt saw threats, as did others, in the mid to late 1930's but they had real difficulty explaining to Congress and the nation why they thought the US should be involved in a European war because much of the nation didn't see the threat in the way the Roosevelt administration supposedly did.

It's not at all clear that the threats to the US from Germany can be encapsulated as merely claiming 'obvious' dangers of fascism. The US didn't go to war with fascist/phalangist Spain. The fascist dictator put in place by the Spanish civil war, Franco, ruled until the 1970's...during which time the US military built and operated bases in Spain, such as the one at Zaragazo, built in 1954 that served both NATO and US interests.