Having lived, like most of us through the cold war, I am for the first time really worried about the possibility of a nuclear conflagration.
The only consolation is that the US is unlikely to respond with nuclear weapons. North Korea is a one shot country. If they fire a nuclear weapon. The Americans should be able to blow it up before it reaches its target, that will not remove all the danger but it will help to mitigate it, but will respond with conventional weapons using surgical strikes by rockets and drones that will take out everything that matters in North Korea, its leadership and its key government and military control centres.
The Americans are not fools, well not since George W Bush ceased to be President, they will have been planning for such an eventuality as this for years. In a perverse way it could almost be a good thing. It would remove one of the worst governments on earth and quite literally liberate the starving and oppressed people of that country.