No that force is symbolic, engaging those 40,000 means engaging the whole US. Just as killing 3000 on 9/11/01 brought about the termination of the Talibans and the world wide hunts after El Quaeda. That is why NK wants the US to withdraw and SK does not. Eventually, they will reunify, but the north economic conditions must improve by a lot before that can happen, otherwise, a unified Korea will go down the drain, instead of starvation just in the North, the whole country may collapse economically.
Zeev