"Taiwan doesn't give us anything"
Of course not, but that is not why there are US carrier fleets nearby. Those fleets are nearby to ensure that Taiwan is not absorbed in to China, which could then cut off supply to The West globally, which would be a major catastrophe for IT in general and all those fancy gadgets DARPA likes to get its hands on like, oh, hypermissiles at a guess. Or all those fancy self-piloted "assistants" that are supposed to be delivered with every new F-35 at some point in the future.
Trump appears hell-bent on not spending a dime on anything. He's missing the fact that, if the USA has the economic and international situation it enjoys today, it is because it is present on the seven seas and the five continents and ready to be aggressive if need be, with the best tools there are. Bring all that military back home and your influence is going to shatter to pieces, leaving someone else to pick up the slack (that someone being Beijing at this point in time).
You really have to be a moron to not see that.