The US and South Korea are on the same sheet of music diplomatically. They oppose North Korea's nuclear development and the Kim dynasty's placement of its self-interest ahead of the welfare of the North Korean people. North Korea detains about 1% of its population in concentration camps. The US and South Korea do not punish political dissent with imprisonment or forced labor.
North Korea envies the attention the US lavishes on its healthier twin to the south. That's why it lashes out with military provocations and drags out even the simplest diplomatic issues for months. The US-DPRK "New York" channel has been dormant for months because North Korea has nothing new to offer. The Kim regime likes to imprison some random missionary when it needs attention but delays release negotiations to extort for foreign aid.
Asians can take responsibility for their own security once they outgrow what ROK President Park Gyun-Hye calls the "Asian paradox" where political cooperation has not kept pace with economic integration. The US will remain engaged in inter-Korean relations until Asian powers resolve that paradox. They can begin such resolution by working on matters unrelated to North Korea's problems. Start with climate change and disaster relief.
The Kim regime in the North makes lots of bombastic threats. It has little to show for decades of hostility to its neighbors and paranoia. This satirically dubbed video of "Pyongyang Traffic Girls From The Sky" may be all the North can muster as a threat. I wouldn't mind seeing hot chicks drop out the sky if they were friendly.