Give two reasons why it was important for the united states to south korea.

Well, this was called the "Korean War", because North Korea was invading South Korea in the mission of spreading Communism, which was the Soviet Union's main order, (the Soviet Union was determined to spread communism to other countries), and the United States was AGAINST the spread of Communism, so in order for the Soviet Union to NOT help North Korea, the U.S. pitched in to help South Korea.

Democracy and darwinism would be my answer.