The US can just “move out of S. Korea” as soon as the DPRK is no more. Win, win all around. All of those US forces get replaced with just a token force. THAAD leaves. US projection of influence in the east switches back to naval power (which the expenditure that had been tied up in the ROK gets redirected into augmenting).
Well show me how DPRK is going to be no more????? Do you think that Russia or China is just going to stand by and let the US do what they want in N.Korea?.... because that’s just not going to happen. .....Neither is going to let N.Korea go anywhere but into their own hands.....or keep it as is....they much prefer Kim stay in power as neither country gives a hoot about Kim or the people....it’s all a “land” issue for them.
This is why Trump and Tillerson keep saying they have no interest in regime change.......they know to even consider this will,and is now causing, China and Russia to defend Kim....
Of course should we leave S. Korea entire....it would only be short order before China and Russia grabs S. Korea.