Those are fairly different though. With Taiwan Ukraine-- the involvement would be clear: Country A invades Country B. US intervenes to fight away country A. Losing here would be a HUGE crediblity blow.

It's very different from "nation building" (which has been proven time and time again to be a waste of time, money, and lives). Losing here is more of a factor of fighting ideologies vs. a distinct adversary.

In terms of training and military hardware the US is pretty much unrivaled even by China. But that knowledge suddenly becomes less relevant if it becomes clear we won't use it when it matters.

One could argue that those weren't US military force failures, so much as policy failures. Peacekeeping and warfighting are very different things.