Woodrow Wilson explained America’s participation in World War One as an intervention of necessity. Peace and stability needed to be provided for in Europe and the world. Many of his fourteen points dealt with the maintenance of territories or the creation of new nation-states. However, he did not argue for the dismantling of the Austro-Hungarian Empire, instead he wished to incorporate them into a peaceful post-war world. In addition, he demanded a reduction of army size and strength and the removal of barriers to free trade and navigation of the seas. Finally, he called for the creation of a League of Nations, to co-operate on the maintenance of peace and prosperity. The fourteen points were generally viewed positively by European people, but negatively by European heads of state. 

The Boxer Rebellion took place in China at the turn of the twentieth century. Chinese nationalist forces had long held grievances against the spheres of influence held by various European nations, and the United States, in Chinese territory. The rebellion was largely fought to remove the influence of foreign powers from China and to dispel Christian missionaries who were attempting to convert the population. The Rebellion ended in defeat for the Boxers and an increase in protected trading rights for the Imperial powers in Chinese territory. 

The America First Committee was set up in 1939 and 1940 in order to prevent the United States from becoming embroiled in the “European war.” The committee argued that President Roosevelt was deceiving the American people with promises of neutrality. They argued that Roosevelt was aiding the Allied powers and drawing America closer and closer to conflict with Germany. The America First Committee reflected the general mood of the American public in 1939—the vast majority of whom wished to avoid conflict; however, with the Pearl Harbor attacks in 1941, the America First Committee rapidly disbanded and American public opinion reversed. 

The foreign policy initiatives enacted during the Presidency of William Taft are generally referred to under the phrase “Dollar Diplomacy.” Taft believed that, in order to advance America’s economic and diplomatic interests and encourage global stability, the United States should encourage private American investment in foreign nations.

Vietnam had been a French colony until World War II, when it was invaded by Japan.  After the war, the country was split into two nations, the Communist (and Soviet backed) North Vietnam, and the Democratic (and Western backed) South Vietnam. While America had always backed South Vietnam in the ongoing conflict between the two, in 1964, the U.S. officially declared War against North Vietnam after the Gulf of Tonkin incident. The reason given for this involvement from President Lyndon Johnson and hawks in Congress was that the spread of communism had to be stopped, and that Vietnam was crucial to this effort.

Most associated with the presidencies of Truman, Kennedy, and Johnson, containment was an attempt to stop the spread of Communism to countries where it was not currently the form of government.  The other policies advocated at the time were rollback, attempting to actually reverse new communist government victories, and appeasement, which sought to make concessions with Communist governments to avoid all out conflict.

The Truman Doctrine was announced by President Harry Truman to a joint session of Congress on March 12, 1947. Truman was specifically responding to political unrest in Greece and Turkey, where it appeared highly likely that Communist governments would take power. Truman asserted that the U.S. would financially assist in any way it could to prevent Communism from spreading, but would nit be involved militarily.

The United States was eager to expand its trade markets, and wanted access to Chinese ports. Various European nations and Japan had succeeded in carving out exclusive trading rights to certain key ports in China, which allowed them to block entire regions from US business. The thriving climate of US economic expansionism encouraged policies such as this one, which was proclaimed by Secretary of State John Hay in 1899, in order to open up all “exclusive” ports to American business, and eliminate the granting of favoritism toward certain countries at Chinese ports.

The Open Door policy was rooted in the desire of U.S. businesses to trade with Chinese markets, though it also tapped the deep-seated sympathies of those who opposed imperialism, with the policy pledging to protect China's sovereignty and territorial integrity from partition.

Throughout the 1980s, Nicaragua was involved in a fierce civil war pitting the left-wing Sandinistas against the right-wing Contras. In the mid-1980s, the Reagan administration openly supported and publicly encouraged the Contras as part of their general anti-communist foreign policy. It was revealed in 1987, however, that the Reagan administration had been giving arms to the Contras that were acquired through secret hostage negotiations with the government of Iran, which had a putative embargo during the period.

The Domino Theory was an integral part of United States anti-Communist policy in the decades following World War Two. Many American politicians maintained that if Communism was allowed to spread it would have a domino effect which would cause other countries to adopt Communism also. It was provided as justification for numerous anti-Communist wars, campaigns and embargos - most notably, throughout Central America and South-East Asia.