How might the cultures of Latin America be different if the Spanish and Portuguese never arrived? What kind of culture do you think would dominate the region today?

They would've been much more influenced by the cultures of the Aztec and Incan civilizations. They might have polytheistic religions and focus more on agriculture, as that was especially important to the Mayans. The social structure might also be different, as indigenous people were used in forced labor for years, which caused the white people to be seen as the dominant class.

Probably the indigenious poeple would be the only poeple living there and there wouldnt have been exploitation of their treasures. Nowadays there would be no white people and no European influences on e. g. architecture. On the other hand Europeans brought development and progress to south america, which might have come much later without them.