"Nuclear Taboo" does not exist[0]. It never did, it never
made sense. You can't rely on the belief that rulers and politicians operate on ethics and reject options based on how morally questionable they are. If they ever did, we wouldn't have wars, we wouldn't have war crimes, "collateral damage", "enemy combatants" = any male 12+; we wouldn't have low and high scale corruption, etc.
What exists is what I described above. Everyone knows war, up to and including nuclear, is always possible, but no one wants to go there. There is an obvious termination point: total nuclear war. It anchors everyone's expectations about how far they can push, who they can or cannot threaten with military action. People can run these hypotheticals quickly in their heads. Netherlands asking US, "so what you're gonna do, invade?", US saying "yes, and what then", and Netherlands... conceding, because they can't one-up. Compare: the only reason the war in Ukraine is still hot, is because Russia has nukes, and Ukraine doesn't, so there's only so much any of the allies can do to help[1]. If both countries had their own arsenal, or neither, this wouldn't happen.
So not "nuclear taboo", just an implicit understanding of MAD and where the buck stops, and how it affects who can threaten whom with military action, and recursively, how far anyone can push anyone else in political negotiations. It trickles down to the ASML/China question, too - even if they really wanted to have this deal, politicians in Netherlands know they have to concede to the US, because what else can they do?. They already run the "what if we X" / "then we Y" loop in their heads, hit the ceiling, and know they can trade horizontally, but can't escalate vertically beyond some point because of X, that's because of Y, that's because of Z, that's because of... nukes.
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[0] - https://en.wikipedia.org/wiki/Nuclear_taboo#Debate_over_the_...
[1] - And let's not forget that Putin threatened the world with nuclear retaliation if NATO helps Ukraine too much. There goes your taboo. Not that it existed, unless you forgot that some years ago, USA threatened the world with nuclear first-strike as a possible retaliation for cyber attacks.