As it says on the tin. The US sends weapons/equipment, but no US soldiers. Assume China and the Soviet Union don't send troops to aid the North either. If it's just N. Korea vs. S. Korea, how long can the South last before being overrun?
Immensely weaker. The United States supplied a vast majority of the troops and material that was used in the conflict -- and it's questionable if the rest of the UN would act if the US wasn't willing to put their own boots on the ground.