If China takes TSMC, then make no mistake; the United States will carpet bomb every facility and ASML's policy towards China will not budge. There are no contingency situations in which China steals TSMC's tech; it's something that Taiwan and the United States simply refuse to let happen. The running "joke" in the industry is that TSMC's foundries are rigged with explosives wired to a red button on the US president's desk. The real-world situation isn't that far off.

America would fall behind in this scenario, but ASML will still exist and advanced lithography can continue independent of Taiwan. TSMC is a big part of the puzzle, but the importance of the first island chain is 10x more important than anything TSMC owns.