Nationalism was never a good idea.
Besides, what about the sounds on this disc is NOT Latin American? Maybe you're defining "Latin American" too narrowly, eh? (What IS "the Latin American sound"? Some people on this thread, including Mirror, have been at some pains to point out how different the four names on his list are from each other. Different, not similar.)
To answer this post (rather late), allow me to explain the differences between the four composers I have listed in the poll and why they were important for their respective countries:
Revueltas: A Mexican Stravinsky of sorts. He was ingenious in the way he could meld together very desperate styles of music into something totally cohesive. Not all that different from what American composers like Ives or Copland were doing. Revueltas and Chavez were good friends until they had an argument and split ways. Revueltas wasn't as noted as a conductor as Chavez was, but he was crucial in getting Mexican music recognized to American audiences, which, in turn, made international waves. Revueltas also wrote many scores for Mexican films which also helped him gain widespread acclaim in his country.
Chavez: One of the most important composers to come out of Mexico. Chavez's own composing style is a mesh mash of different influences: Stravinsky, Schoenberg, and the folk music of Mexico. Where Chavez differs from someone like Revueltas, is he constantly experimented with rhythm and musical structure. He was also known to have quite a Romantic streak in him, which is displayed in his
Symphony No. 4. As I pointed out earlier in the thread, Chavez founded the Mexican Symphonic Orchestra (known today as the National Symphony Orchestra of Mexico), which he also directed, and he was also noted for his tireless efforts in promoting Mexican music in the United States. He even made good friends with Aaron Copland who remained a supporter of his music. You can't deny that he wasn't a major force in Mexican music and one that continues to influence Mexican composers to this day.
Villa-Lobos: The most important and influential composer to come out of Brazil period. This is not opinion, this is a fact. Villa-Lobos' importance rests in the music education system in Brazil (which he single-handedly changed forever), but also in the music he created and distilled upon the millions that have heard his music. VL's compositional technique is a combination of many things: an attention to orchestration that he learned from studying in Paris, the exoticism of the sounds from his country (i. e. the usage of native instruments from Brazil, the folk melodies/rhythms from Brazil), and his absorbing different elements from European musical styles like Neoclassicism and the Impressionism of Debussy and Ravel. It is with all of this knowledge, he formed his own style.
Ginastera: Although Piazzolla, one of Ginastera's students, is well acknowledged by musicians and fans as an important Argentinean composer (he recreated the tango for modern audiences), it is Ginastera that remains the "father" if you will of Argentinean classical music. In fact, it was Ginastera that told Piazzolla to go to Paris and take lessons from Nadia Boulanger, who, in turn, encouraged Piazzolla to find his own compositional voice. Ginastera's own style is a combination of Stravinsky and Bartokian counterpoint combined with a deep understanding of the rhythms and folk music of Argentina. Besides his own very distinctive musical style, Ginastera was an important educator and founded the Julian Aguirre Conservatory of Music.