Honestly who expects the US to honor anything anymore? And to that end, neither do we need to honor any promises we make to Americans either. You just have to remember that this is the crazy person you occasionally have to deal with; anything he says is made up and you can make up random nonsense to say to him too so don't take it too seriously. That is just how the game has progressed; keep playing and keep evolving as long as we're winning. No need to flip the Chessboard or do something rash/desperate just because that's how your enemy is feeling.There has been no US military presence in Taiwan since 1979, as was agreed in the Shanghai Joint Communique.
A deterent maybe, but it will have to be much much more clever than the 3 things you mentioned which are all basically going to war. The sad truth is that at the moment, because of the facts on the ground in Taiwan, using the island to push China's buttons is a very easy thing for the US to do and it's very hard for China to respond in an appropriate or measured way. Flying a politician or a handful of soldiers over in a plane is the easiest thing to do and the only way to stop it would be to shoot the plane down, which would be a massive and unwieldy escalation, so to trade barbs in that specific arena is very disadvantageous to China. The good thing is that these actions don't do serious harm but are provacatory in intent and the reason they were done is because the US has run out of options to cause China serious harm so it's down to middle finger gestures. If we respond, we need to respond in another arena that is more equal, or preferably to China's advantage and that will require some very deep clever thought on how to proceed. The main response, however, is to keep growing faster than the US, running down the clock on its global dominance, and to keep making it easier and easier for the PLA to take Taiwan by the day. That's the bread and butter for cutting the US down and it is the undying root of their fears. Anything visual and in addition to that is just the icing on the cake if the CCP can come up with anything.There have more recently been temporary training deployments of troops. However this is the first full time deployment of US troops. That’s a significant, material difference.
A strong deterrent is needed, or next you’ll see outright bases deployed, like in the Philippines or Korea.