if we did get invovled which i dont think we will it is true our ground forces are stretched pretty thin, but. as far as if it did go down and we did back our allie S Korea, their ground forces would be supported by the best airforce and navy in the world, ours. and we would stomp N Korea and China at the expense of a few ships and aircraft and most of S Korea's ground forces, but we would come out on top imho.
but honestly nobody would really win.