No straw man, you said "The US continues, today, to be the only first-strike nuclear nation threatening to (as an explicit policy) destroy civilian population centers in a host of competitor countries as a coercive tactic and if and when it serves US national interest."

You're using present tense with incredibly broad terminology, same for the rest of your post. It's so broad that it's either meaningless or you really think we're currently, actively holding a nuclear gun to everyone's head over every little thing.

If so it doesn't seem to be getting us very far. China should be far more compliant. /s

Now that you've clarified, you're clearly speculating about what the US "might" or "could" do given the current official policy that's on the books. Which is fine, but it's almost purely speculative and counters your previous point.

Do you have any historical examples of the US actively strong-armining an opponent with the threat of a first strike over a political existential threat? How about an economic existential threat? How about cross-domain warfare with the threat of a nuclear first strike? I have no doubt the plans were drawn up by some department of the government, particularly during the early Cold War. But to my knowledge they have never even come close to mplementation outside of the Korean War and Cuban Missile Crisis.

As for conventional existential threats, Syria and Iran, I would hope that if someone managed to mount a conventional D-Day style invasion of the coasts we would nuke them. And I don't see Syria and Iran anywhere on the list (not that I have time for an exhaustive search, page number?), but it makes sense that Syria and Iran be included given prevailing attitudes about Soviet influence in the 1950s. A nuclear exchange with the Soviet Union would have been total war, including those perceived, rightly or wrongfully, to be their client states.