<P> The Anglo - Venezuelan boundary dispute of Guayana Esequiba in 1895 asserted for the first time a more outward - looking American foreign policy, particularly in the Americas, marking the United States as a world power . This was the earliest example of modern interventionism under the Monroe Doctrine, in which the USA exercised its claimed prerogatives in the Americas . By the late nineteenth century the rapid economic growth of the United States increasingly troubled Latin America . A Pan-American Union was created under American aegis, but it had little impact as did its successor the Organization of American States . </P> <P> As unrest in Cuba escalated in the 1890s, the United States demanded reforms that Spain was unable to accomplish . The result was the short Spanish--American War of 1898, in which United States acquired Puerto Rico and set up a protectorate over Cuba under the Platt Amendment rule passed as part of the 1901 Army Appropriations Bill . The building of the Panama Canal absorbed American attention from 1903 . The US facilitated a revolt that made Panama independent and set up the Panama Canal Zone as an American owned and operated district that was finally returned to Panama in 1979 . The Canal opened in 1914 and proved a major factor in world trade . The United States paid special attention to protection of the military approaches to the Panama Canal, including threats by Germany . Repeatedly it seized temporary control of the finances of several countries, especially Haiti and Nicaragua . </P> <P> The Mexican Revolution started in 1911; it alarmed American business interests that had invested in Mexican mines and railways . The United States involvement in the Mexican Revolution, include, among other violations of sovereignty, the ambassadorial backing of a coup and assassination of President Francisco I. Madero and the military occupation of Veracruz . Large numbers of Mexicans fled the war - torn revolution into the southwestern United States . Meanwhile, the United States increasingly replaced Britain as the major trade partner and financier throughout Latin America . The US adopted a "Good Neighbor Policy" in the 1930s, which meant friendly trade relations would continue regardless of political conditions or dictatorships . United States signed up the major countries as allies against Germany and Japan in World War II . However, some countries like Argentina, Chile, Ecuador, Paraguay, Uruguay and Venezuela only joined the Allied side in 1945 . The era of the Good Neighbor Policy ended with the ramp - up of the Cold War in 1945, as the United States felt there was a greater need to protect the western hemisphere from Soviet Union influence and a potential rise of communism . These changes conflicted with the Good Neighbor Policy's fundamental principle of non-intervention and led to a new wave of US involvement in Latin American affairs . </P> <P> The turn of Castro's revolution in Cuba after 1959 toward Soviet communism alienated Cuba from the United States . An attempted invasion failed and at the peak of the Cold War in 1962, the Cuban Missile Crisis threatened major war as the Soviet Union installed nuclear weapons in Cuba to defend it from an American invasion . There was no invasion, but the United States imposed an economic boycott on Cuba that remains in effect, as well as a broke off diplomatic relations, that lasted until 2015 . The US also saw the rise of left - wing governments in central America as a threat and, in some cases, overthrew democratically elected governments perceived at the time as becoming left - wing or unfriendly to U.S. interests . Examples include the 1954 Guatemalan coup d'état, the 1964 Brazilian coup d'état, the 1973 Chilean coup d'état and the support of the Contra rebels in Nicaragua . After 1960, Latin America increasingly supplied illegal drugs, especially marijuana and cocaine to the rich American market . One consequence was the growth of extremely violent drug gangs in Mexico and other parts of Central America attempting to control the drug supply . In the 1970s and 80s, the United States gave strong support to violent anti-Communist forces in Latin America . The fall of Soviet communism in 1989--92 largely ended the communist threat . The North American Free Trade Agreement (NAFTA) took effect in 1994 and dramatically increased the volume of trade among Mexico, the United States and Canada . </P>

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