no... nukes are not for MAD like everyone thinks they're used ahead of massive invasions they're to cripple military installations crippling the opposing nation so they can't launch a counter offensive
Nukes are not made specifically for the Mutually Assured Destruction, but the volume of them that have been produced is what brought the MAD scenario about. Once one person starts firing them off, there is the potential that others will too, and the combined numbers of them being launched and detonating could wipe out everyone.
It's not what they were made to do, but it's what could play out due just to the numbers.
That same volume of missiles means that they could easily come down in areas that are not defended by a defense system.
ans as i said NK's nukes are tiny they're on the same level as little boy and fatman the only reason they did so much damage in WW2 is because all the buildings were made of wood and paper...
Detonating a 10-15 kiloton (the approximate destructive potential of Little Boy and Fatman) nuclear weapon in a modern city or town would be absolutely horrific. Cities are filled with metal, glass, and everything else that become shrapnel, along with tall buildings that could not just spray that shrapnel, but also topple over. That said shrapnel would also be composed of materials that would hold radioactivity, spreading the lethal effects of the radiation. Most towns and common construction methods used in modern housing stresses the use of light-weight, easy to build with materials. They would do little to nothing to protect against the force of a nuclear blast, as this old bit of test footage makes very clear:
Maybe it's due to the passage of time or experience with just the modern day, smaller scale stuff, but I don't think you really appreciate what the level of power is in a blast as massive as 10-15 kilotons. And while we don't know exactly what the yield of NK's weapons are, if they have any sort of modern refinements (which apparently they do, since they can use missiles to deliver them) it's entirely possible that they have megaton warhead capability.
And I agree with Ramjet556. The THAAD is a nice option, but that video doesn't show the defense system intercepting a target coming in at reentry speeds. If it can, cool. But THAAD units would still need to be in a position to counter.