> In my corner of the US (more Republican than one might think) majority opinion is that the Ukraine is an intra-European matter that US/NATO would be well advised to stay out of.

That's for Putin to decide, like it or not. Just like Hirohito decided to bring the United States into WWII.

That's what I mean, this kind of decision is made at highest levels of government, and meanwhile the rest of the country is fed propaganda to drag it along. (The conspiratorially-minded amongst us notice the weak state of American defenses at Pearl Harbor in 1941. If the Pacific Fleet had decisively repelled the Japanese attack US isolationism might have continued.)

Propaganda is one thing, the simple facts by themselves sometimes suffice. I'm pretty sure if the true scope of what Germany was up to had been revealed to the United States at an earlier point in time that they would have jumped in unprovoked.

> The conspiratorially-minded amongst us notice the weak state of American defenses at Pearl Harbor in 1941. They knew that something was up, but not what was up.

> If the Pacific Fleet had decisively repelled the Japanese attack US isolationism might have continued.

No, then they would have been at war. That's with acts of war: they change the status from not being at war to being at war, regardless of whether that is then affirmed by a declaration of war. Plenty of historical examples for this. What the response would have been is anybody's guess but it certainly would have moved the US out of the 'neutral' column with respect to the Axis countries.