S. Therefore, it is fairly evident that U.S. foreign policy certainly aided in worsening the political situations in much of Latin America during the Cold War. It did so by serving as a source of enmity for many nationalist groups that arose to oppose its domination in the area, by attempting to undermine the reform measures of governments erected in place of those that it favored, and by formally supplying weaponry, funding and training to opposing factions that represented U.S. interest. The effect of all of these measures was that they led to greater and greater reactionary measures among the groups that were...

This fact is particularly true of Central American involvement in the Cold War, the regimes that were erected and dealt with insurrections and counter insurrections in El Salvador and Guatemala were among some of the bloodiest in the Cold War, excluding those in Vietnam. Yet it is important to realize that U.S. involvement in these areas only served to exacerbate issues and factionalism that for the most part were already existent, and which probably would have played out with a substantially less degree of extremity than they did with the foreign involvement not only of the U.S. But of the Soviet Union, as well.
References

Brand, Hal. Latin America's Cold War. Massachusetts: Harvard University Press. 2004. Print.