Taiwan would be destroyed in an invasion, TSMC along with it. China would then have a de-facto monopoly on semiconductor manufacturing. This is why the manufacturing needs to diversify geographically.
Samsung technology is used mainly for memories. Why? No idea. In any case, people would have to migrate their workflows which would take time, and then manufacture there. This would cause huge delays / price spikes
There are other chip manufactures in the world too if people are willing to buy outdated technology (like 10 years in the past)
Also intel is investing a lot in manufacturing technology, it plans to be better than TSMC by 2025 iirc. Will it happen? No idea, but they are working toward this. I wouldn’t be surprised if the US government were financing this in some way
> Due to some obscure legalities, Taiwan dropping the claim would amount to declaration of war
Your wording is a bit vague, but it sounds like you have it backwards. Taiwan's dropping of claims to the mainland may trigger a _Chinese_ declaration of war. That comes from certain interpretations of article 8 of the China's Anti-Secession law. Of course China doesn't actually have to declare war in this situation if they don't want to. They could always interpret it differently or they could simply ignore it (China's laws guarantee free speech after all and they certainly don't seem to have trouble getting around that).