Americans have nothing to fear from North Korea. They wont be able to weaponize a warhead (Make it small enough to fit on the top of a missile) for the foreseeable future.
Then they would have to actually have a missile capable of making across the ocean and hitting an American target I put those odds 1000:1 . If their recent satellite launch is an example of what they are capable of Im not too worried.
Now South Korea on the other hand..... They are F*cked if NK can get a nuke 10 miles over the border, and I consider those odds much higher.
But, China would never let that happen. So all NK has is a High School level nuclear program, the Michelin tire man as king, and a nice neighborhood with neighbors that dont want to be reduced to rubble.
You could take NK overnight if you could get China to back a plan and convince the population that they need to hold an election.