North Korea is one of the crappiest countries you can think of. I feel bad for its people. If the leader, the man who should not be named, decided to actually open his borders he would instantaneously find himself without subjects, as all his people would flee North Korea.
OK, so the man who should not be named wisely keeps the borders closed. North Koreans can not even imagine what the life is like in the developed world… or they might become dissatisfied with their leader; the man who should not be named thought of that too, and cut off his country from internet and any opportunity to learn about the world.
What if you really wanted to be famous and have everybody talking about you? North Korea does not produce anything worth mentioning, the life is tough and often the people go hungry. Nobody is interested in North Korea! The man who should not be named needs to keep his people in check. So, he introduced a lofty goal. Think Elon Mask and the migration to Mars. Oh, wait, it is not that. Think if North Koreans could challenge the biggest, strongest country in the world! Mission accomplished, suddenly you are the super star and everybody is talking about you. Wait, What? The biggest and strongest country is afraid??
What U.S. should do is to get prepared for everything… and then just ignore the little and inconsequential North Korea.