Spanish spoken in the United States today is a blend, a dialect of the various regions of Mexico but also that of Puerto Rico, Cuba, the Dominican Republic and countries like El Salvador, Panama, Colombia and Peru. Along with the diversity of language, this has also brought American society a mosaic of cultural traditions which have since been integrated into mainstream culture, and greatly diversified the belief system and practices of the Catholic church in America.
You might want to consider the way in which certain countries or groups of people have formed a definite attachment with a certain state or locale in the US. For example, I live in Bolivia, and Virginia is known here as "la segunda Bolivia," or the second Bolivia, because of the way that there are so many Bolivians that have emmigrated there or work there. This of course impacts this particular part of the US.
Different areas of Central and South America contribute to the cultural diversity of the Hispanic peoples in the United States by bringing different cultures, different practices, and different backgrounds with them when they immigrate. To assume that all people who live south of the Rio Grande River all the way south to the tip of the South America continent are the same is an insult to the rich history and creative traditions of those cultures.
One place where I really notice the varied diversity is in food culture. I live in a large urban area where I can get any and all kinds of Hispanic food -- but my family and I have learned first hand that Mexican food is different from Honduran food, and a local Peruvian restaurant is one of my son's favorite places to eat!
One factor relevant to U.S. immigration from South America is that there is great diversity within the populations of South American countries. For instance, Argentinean populations comprise German, Spanish, Italian and native Argentine ethnicities. So when Argentines immigrate, they bring a strong ethnic and cultural mix to the U.S demographic.
They have contributed to the knowledge that not all Spanish speaking are from the same country. Along with this, there is a growing understanding of the many different nations that are in Central and South America. In addition, they have brought their cultures with them, which includes, music, works of art, foods, and many other cultural influences. Finally, as the economy of places, like Brazil gets stronger, more attention is given.
A surprisingly large number of Hispanic immigrants to the U. S. have come from Central American (excluding Mexico). One recent estimate puts the number at 3 million, or roughly one percent of the total U. S. population. Although non-Mexican Hispanic immigrants are not as visible as immigrants from Mexico, their presence in larger cities is indicated, for instance, by the number of restaurants they own and operate, where they share their cuisine and culture. Here are two links that are relevant to the statements just made:
My hometown of DeLand, Florida and the area just north of the town bills itself as the "Fern Capital of the World." More fern is grown for resale in this single 30 mile area than anywhere else on the planet. Because cutting fern is a dirty and back-breaking job, it was difficult to find workers willing to do the chore for the low wages offered. Enter the immigration of Mexican fern cutters. Thousands of Mexican men, women and children moved to the area beginning in the early 1980s, offering the area a Hispanic cultural diversity not found in this part of Florida. Additional workers from Guatemala and Honduras have followed, offering an even wider cultural flavor usually found in only much larger cities.
Basically, they have done this by not being Mexican. The majority of Hispanics in the US are of Mexican origin. They are not really monolithic since different regions of Mexico do have major differences. But when Central and Southern Americans come in you get different foods, different accents, pronunciation and dialects, different music and other such differences. This makes the Hispanic community much more diverse than it would be if almost all Hispanics were of Mexican descent.