A war with China over Taiwan, for example, wouldn't be a total war (at first, god willing). But it would be one that would have the US pitted against a foe with better technology than we've ever faced, even if they can't easily project much non-nuclear force into our territory.

People in the 20th century didn't think WWI would happen, because it would be incredibly stupid to blow up yourself and your trading partners. We did it anyway, and underestimating our capacity for self-destruction invites it.