Brazil is a market on itself. Just check out our demographics from 1946 to now;
Argentina, Paraguay and Uruguay can have a Mercosur grouping, along with Chile;
The other South American countries might be grouped in an Andean Community, with the exception of Guyana and Suriname, considered caribbean until the creation of Unasur (which will group everyone listed here so far);
Mexico, Central America and Cuba can be considered a single market (remember, all other Latin American countries have normal commercial relations with Cuba). The rest of the Caribbean should be separate from them.