...vanquishing the late-60s/early-70s movements favoring popular insurgents over existing oligarchies and dictatorships.
A good quick summary can be found at
http://www.icomm.ca/carecen/page74.html :
Theodore Roosevelt's ascension to the presidency led to a more interventionist U.S. approach throughout the Caribbean. Roosevelt derisively referred to Latin Americans as "dagoes" and believed they were incapable of governing themselves. In 1903 the U.S. helped Panama break away from Colombia and begin the process which would lead to the building, by the U.S., of the Panama Canal. Roosevelt called for the use of a "Big Stick" to insure a climate in the region congenial to American business operations.
In 1905, President Roosevelt promulgated the so-called "Roosevelt Corollary" to the Monroe Doctrine, authorizing U.S. military intervention in the affairs of the nations of the Caribbean Basin to suppress revolutions which might threaten the stability of the region or the ability of the country in question to meet its international financial obligations. < IE pages 38-39>
Diplomatic historian Walter LaFeber has pointed out that the Roosevelt Corollary turned the Monroe Doctrine on its head. The Monroe Doctrine was designed to prevent foreign interference in the revolutions of Latin America. The Roosevelt Corollary authorized outside intervention, so long as it was intervention by the United States! According to LaFeber "To argue...that the United States intervened in Central America simply to stop revolutions and bestow the blessings of stability tells too little too simply. The motive for Washington's policy in Central America was not to stop upheavals, but to promote U.S. interests. In El Salvador, for example, North Americans-both in the business and the diplomatic community-continually encouraged a revolutionary faction between 1906 and 1913 because they knew the faction was more pro-United States...than the actual, legitimate government. " Over the next thirty years, under the guise of "gunboat diplomacy", "dollar diplomacy", and Wilsonian Progressivism the United States would intervene militarily and diplomatically again and again to install allies into power and to quell revolts.
Augusto Sandino's Nicaraguan revolt in the 1920s marked a serious challenge to U.S. policy. Sandino aroused the poor of his country to confront an elite backed by the U.S. When the U.S.-supported regime appeared on the verge of collapse, American marines were rushed in. The Americans helped create a politicized military which would rule Nicaragua for half a century.By the 1950's Central & South America were filled with countries run by "our son of a bitch" (Franklin Roosevelt's famous phrase regarding Nicaraguan dictator Somoza {father of the one who was overthown in 1979}). That changed slightly with the revolutionary movemets by Fidel Castro, Che Guevara, and others. One could also argue that the poicies of 77-92 were what they were because our involvement in Vietnam precluded armed intervention in Central America in the early 70's.
The 1977-1992 policies can be dressed up as reactions to Vietnam and anti-communism, but its real roots go back over a century. Hell, you can go all the way back to William Walker (
http://www.calnative.com/stories/n_walk.htm), before the Civil War.