Obviously there were Hunter-gatherers and agriculturalists on both continents, but with the exception of the Mississippi valley I can’t think of a large, city-building culture from North America that rivals the Aztecs and Incas. Also, metallurgy was pretty advanced in South America while practically nonexistent beyond bronze in North America. I would think the deserts, jungles and mountains that make up much of South America would hinder a society’s ability to advance.