If China really wanted to reclaim Taiwan how likely is it that the US really go to war?

I’ve convinced my mind so much that this WON’T happen, that I’m not sure how to answer it.

It would depend on what kind of reclamation and how willing Taiwan was. If it was completely unprovoked and premeditated attack-you could probably say goodbye world as we know it (IE US-PRC War).

It is not likely.
The US does not have to go to war with China.
The US buys too much stuff from China and owes China too much money. If the Chinese invaded Taiwan, the first thing the US would do is embargo any goods from China, and freeze payments on the debt. China would have an immediate cash flow problem and any spoils they took by reclaiming Taiwan would not offset it.
Plus, it would immediately drive Russia, and India solidly into the American camp with the same consequences.
In the short term, it would be tough on American businesses that own or lease factories in China and Taiwan. But money that was no longer being shipped to China, would quickly enough be used to begin domestic manufacturing. Jobs would be created, people would start buying again, and the economy would grow, while China would be left griping to an unsympathetic world that the US is not paying interest on their bonds.
Anyway, the list is endless why China won’t do it.
However, as a side note, the president is overplaying his hand by sendling a carrier to South Korea. The Chinese do not want a greater American presence in the area, and who knows what they will do to assert themselves. Sometimes “face” and/or “national pride” make people do stuff that is not in their interests….

I believe @josie has given you a great answer. There is certainly some line that Chinese land grabs can’t be allowed to cross. Open empire building as Hitler had in mind when he invaded Poland must be challenged and all out war is the challenge to it. But an economic war would be sufficient to defuse a Tiwan land grab, and knowing that, it is unlikely China would grab Tiwan. More likely, as they ramp up their economy and transition from strict communism toward a market driven system, they will try to reconcile amicably with Taiwan.

Beijing will eventually assert its supreme influence over Taiwan, but it will probably involve a lot of subtle power-play and political/economic shenanigans.

Don’t think it’s off their agenda though, oh no, its high up on a looooong list.

It would be up to the UN, not the US.