The Monroe Doctrine doctrine was the ultimate expression of Manifest Destiny which applied to what we consider today to be North America of which a large portion was under the control of Mexico many people seem to forget this fact for some reason.
Ever since it was put fourth in 1823 we have more or less followed it to this day
most Latin American nations are safely in the United Sates pocket and that is how we like it Venezuela is just an annoying blister like Cuba.The US says jump almost every Latin American leader says "How high senior?".
http://en.wikipedia.org/wiki/Monroe_Doctrine
Why do you think they invaded Panama back in 1989? They wanted to rid of Manuel Noriega not because he was involved in drugs they could have cared less but because he was going to allow the next major refurbishing project on the Panama Canal go to a none US firm Manuel Noriega was not going to play by our rules.
MS13 is not a Mexican gang it originated in El Salvador and is mostly made up of El Salvadorians they and Mexican gangs are huge rivals they hate each other the Mexican cartels deal with whoever controls the turf which is usually MS13 because they are the most violent and the Mexican cartels will employ Spanish speaking gangs though most of that "work" is in Mexico they go on a vacation so to speak MS13 goes where they can make money.
Actually most Latin Americans like or a are neutral towards Americans in my experience.The Cartels have power in Mexico and some parts of Central America the South is another Story all together.If you are in Columbia it is either the Colombian Government or FARC depending on what part of the country you are in same applies to most other nations to some degree.