I disagree. The coup to overthrow Allende allowed Pinochet to stabilize that country. Our support for a strongman in El Salvador kept the commies at bay, as did our support for the Contras in Nicaragua. All 3 of these are in far better shape today than they would have been if we let the red tide roll.
You presume that there was some period of time when central and S. America was a bastion of stability. It never was.
El Salvador has a growing insurgency and crime problem, Nicaragua also has growing problems of internal unrest.
All three are happily exporting there poorer population to America.
And China, is extending her influence through economics.
The old ways of coups and covert ops to destabilize opponents is being replaced by the new economic war.
America may one day wake up to find that she has lost much of her influence to China.
This is very much the case with Africa, poverty stricken but rich in resources needed by a modern growing market.