I think that there is also a sense among other countries in the world that these countries are undeveloped or unstable. Unfortunately, there is a tendency to look down on South American countries. This certainly seems to be the case in America. We do want to take our factories there to outsource if we can get cheap labor, but we don’t seem as willing to trade with them except for produce.
I would agree with the previous post in that the historical divisions between Euro/Creole elites and other groups of people probably are at the root of the matter. I would go even further and point out that many Latin American countries had a very complex hierarchy loosely based on, but not necessarily determined by race. People of mixed ancestry, including Europeans, natives, and Africans sometimes occupied different strata in their societies. These different groups certainly contributed to vibrant, diverse cultures even if they made the formation or articulation of anything we might call a "mass culture" rather slow in coming.
I think there are a number of possible reasons for this. Perhaps the major one is that their economy was based on indigenous people working in their traditional territories and in their own traditional groups, albeit for Spanish/Creole landlords. This made it so they did not really have a good chance to lose their cultural identities and become part of a mass society.