One of our Boomer subs can put about 240 250 kiloton warheads on any nation. That will destroy them. We have many of these subs.
And in large part because of W Clinton efforts or acquiescence at the UN in 1993, Russian and Chinese subs (or others) can launch whatever they want from 12 nautical miles of our coastline.
From launch to TOT is literally about a minute to many of our largest cities.