Here is some information that will help
Pros
1) US shows that they are dedicated to the policy of containment: During this time, the US federal government adopted a policy of containment. This concept was all about stopping the spread of communism on an international scale. This helps to show why the US got involved in Korea, as they were trying to help South Korea from being taken over by a communist North Korea.
2) Helping South Korea resulted in the US getting a long term trade partner. This continues to this day, as we get many different products from South Korea (like Hyundai cars).
Cons
1) This was another foreign overseas war that many Americans did not think was important to the US. They saw this as an overreach of power.
2) Thousands of American lives would be lost fighting in the Korean War.