What does sounding like a native really mean? In Spain, a number of people learn Aragonese, Asturo-Leonese, Basque, Catalan, or Gallego, as well as the country's official language, castellano (Castilian Spanish). Many within the populations of Latin America are bilingual speakers of Spanish and another, indigenous, language—Spanish serves them as a means of communicating with people outside of their group or region, often for the purposes of commerce.
Español (ehs-pah-NYOL) means “Spaniard” (from Spain, Spanish), and castellano (kahs-teh-YAH-noh) means “Castilian,” the language you call “Spanish”—the official language of Spain.
Because Spanish is spoken in so many countries, sounding native is hard to define. If you were asked to teach someone to sound like a native speaker of English, which native speaker would you choose—an American professor of English at Harvard or a police officer working on the south side of Chicago? A Londoner who speaks with a cockney accent, or an Aussie from Melbourne?
Whether you speak a particular Spanish dialect or not, if you were not born within the boundaries of Spain or a Latin American country, you will always be a gringo (GREEN-goh). In most places, “foreigner” is all that it means, so, for example, a person born in Vermont to a Chilean couple is still a gringo. His Chilean family, however, may actually use the term gringuito (green-GEE-toh) to demonstrate affection.