North Korea is not in the same league as the US, no country is when it comes to conventional military superpower. We aren't talking about foreign insurgencies and enemies that are indistinguishable from civilians - the US has no equal when it comes to the conventional power - especially in the air and in the seas, where it counts if all hell breaks loose. The F-22 Raptor is unparalleled, not to mention the bomber groups. It's not a secret, the US doesn't hide their capabilities, the North Koreans can hear the sonic booms of fighters on the border and they can see the naval battle groups operate seamlessly with each other and with their allies (specifically Japan and South Korea). Kim Jong Un is using the same playbook as his father in terms of trying to get concessions under the threat of military confrontation.