America's foreign policy goals changed for several different reasons. One of the reasons why it changed were because of new threats to democracy. For example, World War II (1939-1945) brought in the reign of dictators all over Europe. Along with this, the US was attacked by the Japanese Empire at Pearl Harbor on December 7th, 1941. These different factors caused America to get involved with World War II to help the allied powers.
After World War II, the US wanted to stop the spread of communism. This policy, known as containment, reflected America's fear of the growing power of the Soviet Union (a communist superpower at this time). To stop communism from spreading, the US got involved in foreign conflicts like the Korean War. The US was trying to stop communism from spreading into South Korea.
