Willie Tomg posted:

Using nukes on metropolitan areas as a component in a strategic exchange is one thing, but in the case of China in particular and also Russia I find the most primarily concerning use in a defensive posture as part of say, intervention in the South China Sea or Crimea.

More knowledgeable folk than me have pretty aptly demonstrated why first-striking the US mainland is a pretty bad idea for anyone, and how second-striking is not terribly credible from any forseeable party, but what if China uses some of their limited stock to erase two or three carrier battle groups throwing their heft around in waters they claim? That is a much more plausible and thornier deployment of those weapons than outclassed subs taking a shot at the west coast USA, IMO.