Far beyond the value of TSMC, Taiwan is the lynchpin of the first island chain [1]. Taiwan remaining friendly to US interests is crucial to the integrity of the first island chain and thus the US island chain strategy[2]. In the event of conflict with China, control of the first island chain would allow the US to effectively interdict all maritime trade to China by denying access through the chokepoints created by the first island chain. This is frankly much more valuable to the US from a strategic perspective than TSMC (though TSMC is obviously very important).

You can also note the importance that Chinese planners place on this as well by looking at the Belt and Road Initiative, in particular the land-based projects that aim to connect China to European markets via rail [3][4].

1. https://en.wikipedia.org/wiki/First_island_chain

2. https://en.wikipedia.org/wiki/Island_chain_strategy

3. https://en.wikipedia.org/wiki/New_Eurasian_Land_Bridge

4. https://en.wikipedia.org/wiki/China%E2%80%93Central_Asia%E2%...