To be honest I doubt the US has the resources to fight on the Korean peninsula right now. Spread to thing, and our material is breaking down.
North Korea is a thorn in China’s side, if there was an easy way to get rid of the problem, the Chinese would do it. Their nightmare is to have millions of NoKo refugees streaming into China.
South Korea is in the same predicament as well, if they somehow beat NoKo, then they will have their own issues with refugees.
Eventually South Korea and China will have to become partners to solve the North Korea problem.