Why did the United States enter the war in 1917?
The United States joined the Korean War because the US feared
that all countries in Asia would be turned to a communist country.
At the time of the Korean War, China was a huge factor because
China supported North Korea. If the United States did not support
South Korea then the domino effect would have been put to
effect.
In other words.. The United States joined the Korean War to
resist communism from spreading.