Mister President, we must not allow a Mineshaft Gap!
thank god we have all that set up then.
We don't know that nobody does. We don't even know that the US doesn't. Putin could have one, and China, Israel, England, and France seem likely. Japan and India are possible. North Korea? Iceland, if they could afford to dig one, wouldn't need the nuke. Peru might have inherited one from deep time. Egypt, likewise. Turkey has lots of underground cities already dug that mainly only need wiring.
I don't think anyone in power would enjoy living the remainder of their life underground in a bunker. So this is implausible as a scenario.