After WWII, President Truman developed a foreign policy designed to contain the expansion of the Soviet Union and help countries resist communism. This policy received the name of the Truman Doctrine.
The Truman Doctrine had certain benefits. For countries that struggled with their fight against the Soviet Union, this allowed them to have the financial support of a wealthier and more powerful nation. This was the case in Greece and Turkey. It also led to the development of NATO, an important international organization.
However, the doctrine also had important pitfalls. Many people believed that the doctrine was designed to help Truman gain popularity, as opposed to actually causing change in the world. Many others argued that the governments Truman wanted to support were not necessarily better for locals than communist governments. Finally, others believed that the United States should not involve itself in the internal politics of other nations.