For GPUs, I agree that you currently have to use TSMC. But if TSMC were to charge 30% of profits, you would almost certainly see a migration to other fabs which would harm TSMC's long-term profitability.
Give it 10 years and a lot of engineering time, maybe half a trillion USD and you'll get the equivalent in the mainland US. Until then, it's more convenient to use the US military resource to protect Taiwan from PRoC.
