As it is well understood, speculation is the mother of all fuck ups. This applies as politics as much as it does to everything else. Nonetheless, I will make a wild guess based on the limited information we have from the N.Korean front since more or less, everything we are being fed is bullshit.
The U.S has a long history of messing with other countries when they want to get in control. They don't do this by just landing troops somewhere (taking over Rambo style) but rather employ techniques that take the enemy from the inside. If you doubt any of this just take a look at the history of most Latin American countries or every other situation the U.S has engaged in armed combat. The first step always involves some political maneuver from the inside in order to make war less expensive. Surely, armed forces are deployed but only when resources are in play (see Iraq). When it is just geopolitical positioning, coups do just fine.
Which bring us to the second possibility. Keeping hands clean from the situation. While a coup might be orchestrated by the U.S, the forces that will be actively advertised are going to be anything but American. In all likelihood "mysterious" occurrences will have major North Korean figures fleeing the administration or getting assassinated while South Korean forces gain ground in some key positions. Japan will surely aid and America will arrive last, putting the cherry on the cake, "liberating" the oppressed North Koreans.
Even if nothing of all these happen, I strongly believe that a similar scenario will be played out or at least attempted in order to keep the eyes turned on that specific part of the world while the American political divide grows larger. The national debt has hit all time records, the petrodollar is getting smacked by the Chinese and as we all know, war is always good business for United States when it comes to turning things around (especially the worrying heads of the citizens). War is perhaps the most lucrative of all enterprises when it comes to both politics and economics, yet very few a ready to acknowledge its impact. They rather believe that America is defending the "liberties" of the citizens of the world, policing around for a better world. I guess American pop-culture with superheroes has given this idea. Who would have guessed?

Like I said above, this is a wild guess. I would understand perfectly if someone shits all over this post since I have no evidence, just vague correlations from the bullshit news they are feeding us and some weak clues from the historical record. I really do hope to be wrong and this thing does not escalate or else things will get fucked up for a lot of people really fast, really soon.