why? they haven't lost any war there
If the goalpost is "being an impervious shield". I think a more reasonable expectation would be to prevent or respond to a Kuwait situation and keep shipping open. Obviously that second one is a huge failure.
But we have only seen bombings and angry tweets. The US military is capable of quite a bit more. It's a terrible path to go down (and we may do so in about a month), but we haven't seen the full capability of the military because the orange guy in charge only wants to do bombings and threaten genocide.
It wouldn't be worth disputing the semantics of what kind of black mark this is for the US as a global power, except that you use it to conclude there is no point to maintaining bases in the far east. If you think they don't matter, just look up any discussion of Chinese warplanning.
From what I've read, there are two likely Taiwan scenarios:
1. China targets US bases and ships before sending transport craft across the strait. Sending transports without that first strike would be suicide. Unless this reporting is wildly inaccurate, it is a very clear acknowledgment of the impact of the US military presence abroad.
2. China blockades the island. This opens the door to a Crimea-like soft invasion whose outcome depends on the international response.
In both cases, bases in theatre play a huge role. You talk about "day one" - in either scenario above it's not a one-sided first strike where the plarf wrecks US bases and ships and the pla dances into Taipei. Recall how much advance warning the US publicly gave of the Russian invasion?
When you are deciding on your takeways from the Iran conflict, remember that it's a bombing campaign and not reflective of a full near-peer war.