TSMC is absolutely critical for 'frontier' silicon but:

1. In a China/Taiwan conflict, China's not getting TSMC output either - Bear in mind that I doubt China would ever want to destroy TSMC though, so I'm talking about a naval blockade rather than artillery destroying the fabs.

2. Although SOTA chips are off the table, we could get older process node stuff. We could still build say, 2015-era chips. We had great missiles in 2015.