> The options
The obvious option in event of PRC control is everyone deferring to mutual leverage, where US controls fab inputs, TW controls outputs, PRC negotiating access to % of high end production by controlling island. Meanwhile buys both US and PRC time to secure independant semi chain, TW gets to still profit off semi, much like pre techwar arrangment. That's the strategically rare win-win-win scenario where everyone gains / avoids loss vs having accessible leading edge setback 20 years. Of course PRC wins most in this arrangment, and US/TW relatively loses, but if PRC wins in TW scenario vs US, that's going to be least of worries / concessions. The least obvious option is US deciding to scorch earth tech that supports their most competitive high tech industries, responsible for huge % of competitive advantage, especially if that leaves PRC the biggest producer of mature nodes (where things are trending). Even less sensible considering long term timeline after which experts believes PRC can reach semblance of semi parity.
This is short/medium term balance / interest calculation irrespective of the deal - which I didn't comment on - substantial capacity won't shift off TW in the timelines US forecast PRC will make move. Leading edge isn't particularly relelvant to defense hardware ends which use mature nodes, nor does anyone project long fight with how irreplaceable modern platforms are. It's why PRC (and chip partners US is trying to coerce into export controls) views Oct chip curbs as attack on their commercial sector, not military since PRC also have small batch 7nm production capability.
> TW also sees its best interests
It's also obvious "best" TW interest is to hedge having continued leverage over being leading ledge supplier regardless of who wins. There is no scenario where giving away their silicon dominance makes sense, unless coerced to, which is why US had to unilaterally announce export controls - because CHIPS4 partners weren't biting and actively pushing back. Least of all because no one is sure TW can win local war against PRC. Wealthy TW industrialist/elites/chip talent would rather be wealthy under PRC control after war then be fruit farmers because their industry got glassed. Read between line of Morris Chang stating US efforts to reshore chips manufacturing doomed to fail - it's not commentary on US talent - but TW isn't ceding industry to be Americanized. IMO don't expect these plants to launch without hitch. Prolonged war is probably least in TW interests because island simply can't sustain past a few months on domestic resources. There's reason TW defense posture is not prepping for prolonged war like US wants, deep down leadership and industry knows best interest for TW is to survive short/sharp war as developed economy and work with whoever wins.
> strengthening US defense's tech position
Except, again, TW offshoring leading edge fabs doesn't substantively strengthen US defense indy that depend on mature nodes with respect to PRC war. As stated, US fabs will STILL depend on TW inputs for forseeable future - it's not just ASML that's bottle neck - niche suppliers and expertise will be stuck on TW long term. Also consider "partners" pushing back on unilateral US curbs or SKR, JP building out their own indigenous defense industry - very few are actually interested in giving/strengthining US further leverage especially at their cost. And let's be real, fabs aren't going to be rebuilt on TW if they get leveled when they can be reconstructed in more secure locations.