I don't know where you got the idea that the US will not go to war to protect the US economy, national security, or military capacity, but you are severely misunderstanding the situation. That is why the military exists. We spend the amount we do on the military to support American economic dominance and define the rules on how world trade happens. The reason we are not doing more for Ukraine is because they are not very important to the US, outside of being a buffer against Russia.

Ideas like "protecting democracy" are used to sell citizens on wars they don't care about. The full destruction of TSMC is likely preferred over a Chinese dictated world technological economy. The truth is, if one side has TSMC chips and the other doesn't, what we're talking about may necessitate a total war.