The atmosphere differs from country to country. The most obvious factor dates back to colonial times. Latin American countries that were conquered by the Spanish still have Spanish as their official language. Brazil is the only one in the are that Portugal possessed, so that is why Portuguese is spoken there.
The islands in the Caribbean have a bigger variety of colonial histories, with a lot of Dutch, French and British influences there.
Another factor would be the "coast" vs "mountain" factor. Peoples from the Andean regions (Peru, Ecuador, Bolivia, Colombia) tend to be a bit more introverted than the people from the coastal areas.
Then there is the "race" factor. Country with a more extensive history with African slaves has a larger black population, which often als reflects in the languages spoken, the music that is played and the food that is eaten. Countries with a larger indigenous population (like Peru or Bolivia) are strongly influenced by this ancient heritage.
So there you go... A lot of things.. And then there is more...