It took them years to pull it off. If a such a project were to begin in Taiwan, intelligence on the ground would be aware of it. If they want to try to get one started, then fine. China will act to prevent such a project from becoming successful.
How could China prove that was what was happening? North Korea got away with it and Iran appears to be. If China attacked without comprehensive proof that Taiwan was building a nuclear arsenal, the US would retaliate.
Not at all.
We probably let some Muslim to set off a bomb in London, just to test the water. We're adult and play seriously.
No sane person would give nuclear weapons to terrorists. First of all, if they were traced back to that country, the world would turn on it immediately. Second, terrorists can't be controlled - they'll use their weapons as they please. There are a lot of Muslims in the world angry at what China has done and is doing in Xinjiang.
Uranium does not grow on trees, so Taiwan has to get their weapon from some where.
Taiwan has a supply of uranium for its nuclear plants - it signed a deal with Australia to get more last year. Yet I don't see any Chinese missiles raining down on Canberra or Sydney.
But, what's the difference protecting Taiwan long enough, so they develop their own WMD than actually building one for Taiwan. The end result is the same. I am sure US is smarter then that.
The US isn't going to stop protecting Taiwan because it might use that opportunity to make WMDs. If it
knew Taiwan was doing that it would, but it wouldn't because China made the accusation.