Peron set up an extensive social democratic structure in Argentina when he was in power as some sort of an odd sort of Left populist. Chile had an extensive social democracy already set up even when Allende took power. Chile is already a pretty socialist place, but the newly elected President Bachelet has promised more socialist changes. Leftwing generals seized power in Peru in 1968 and undertook a number of leftwing changes.
Socialists were in power in Guyana for a time and Cheddi Jagan, a socialist, is still a major political figure. Even much of the opposition in Venezuela consists of a large formally socialist party. In Brazil, the opposition is in the process of throwing out the Left government via a phony legislative coup. The opposition party that doing this has “social democratic” in its name and social democracy is stated as one of its principles.
The Left is currently in power in Chile, Uruguay, Brazil, Peru, Ecuador and Venezuela. They were recently in power in Argentina and Paraguay but were overthrown by a legislative coup in Paraguay and probable economic sabotage in Argentina.
The Right is in power in Colombia, but they have only stayed in power by killing 200,000 people. The Left is kept out of power via death squads and the army and police. Furthermore, the Left is armed to the teeth.