The USA in Korea demonstrated that they had the will and the means to contain Communism.
Korea was a success for the policy of containment as South Korea did not fall to Communism despite the North Korean invasion.
Containment proved to be a limited policy as the USA was unable to defeat North Korea which remained Communist following the Korean war.
Korea highlighted division in the US leadership.
The cost in casualties for the USA was very high during the Korean War.
North Korea remained a communist nation and South Korea became a free republic.
Korea soured Sino-American relations for the next 20 years.
The War destroyed Truman's popularity and he didn't run for President again in 1952.
The USA looked aggressive and indecisive and almost sparked off World War III with China.
As a result of the Korean War the USA signed defence treaties with Japan and the Philippines.
The Korean War set the stage for US dominance of the UN during the Cold War.