Obviously if deterrence and containment are in the picture, there's something to worry about. You deter and contain that which you are worried about, what would be the point otherwise?

North Korea exists... we all wish it didn't, but it does. So does Iran. The extent to which the US - or anyone else - can tell them what they may or may not do inside their borders is very limited: the US is not in a position to tell them what they are or are not allowed to do. Action outside their borders can be contained and deterred. It's liable to be messy around the edges at times, as these things generally are.

What's the alternative to deterrence and containment? Do we want to "do regime change" in North Korea, or Iran?