This is nothing new and in fact has been going on for years.
Think of it like the cold war. Two sides making empty threats to each other and showing off its "Nuclear power". Yet not a single battle was fought during it.
Same thing here, the U.S. is trying to scare North Korea into backing off South Korea, and North Korea is trying to scare the U.S. into backing out of their affairs. Neither side has acted yet, and might not act for many more years.
You can rest easy knowing that when push comes to shove, the U.S. is going to have South Korea and all of NATO behind them, while North Korea will have pretty much no one. I will say the thought of North Korea having nuclear weapons is a scary thought.