Since the Korean Armistice until recently, the U.S. & South Korea were absolutely united in their policy goals re: NoKo.
Once NoKo developed nuclear weapons capable of hitting U.S. our policy goals began to divide. No longer is the U.S. policy in Korea solely about the defense of SoKo. Now the U.S. priority is the defense of the U.S. - and SoKo & NoKo know it.
NoKo has been playing the U.S. for fools for years - knowing that any action against NoKo would require SoKo cooperation and SoKo would never cooperate with a preemptive attack.
I can't blame Presidents before Obama for trying to reach a more normailized relationship with NoKo - which was to no avail since NoKo reneged on just about every agreement.
I do blame Obama's 'Strategic Patience' policy. It was clear that it would be only a matter of time before NoKo had nukes capable of hitting the U.S. I also Blame Trump for not taking preemptive action against NoKo with or without SoKo's cooperation.
Basically, we are up shit's creek. Now that NoKo has the nukes they can strike anywhere (except th eU.S.) without fear of nuclear retaliation by the U.S. They know that we will not be willing to get into a nuclear war to defend SoKo or Japan. SoKo is lost.
The ONLY thing I can think of is to give SoKo an arsenal of Nukes that they have independent control over. Let NoKo & SoKo nuke the shit out of each other if they want - but keep us out of it.
Giving South Korea Nukes is a terrible idea.
The fact that South Korea is highly compromised by North Korean intelligence, not with standing.
The potential for miscalculation leading to Nuclear War is far too high.