The problem between the U.S and North Korea lies essentially with the leadership of both nations, as does the solution, the key to which is to bring both leaders closer together.
How to do this? What I would recommend is to drop them both onto an otherwise unpopulated island far distant from any other distractive humanity. In such a situation each of them would of necessity need to depend upon the other for the audience each so desperately needs, thereby ensuring neither would threaten the other -- nor us for that matter.
Now, by no means would we do this heartlessly. Once a month, basic rations would be parachuted in, along with orange hair dye for the one, and extra sharp clippers to tend to the "do" of the other. Also, annually, the one would get a symphonic recording of "Our Supreme Emperor's Godliness," accompanied by the soundtrack of a hundred intercontinental missile launches, and the other a Triple-X size crimson necktie and a jacket with conveniently no extraneous front buttons to bother with.
In the meantime, we common citizens of both nations could finally bask in the peace now currently threatened by both leaderships, and perhaps even actually experience the thus far denied "fellowship of man," and even approach realizing the teachings of our Prince of Peace.