Emigration from Spain to their new world was relatively low. The estimate seems to be that only around 0.42 million people moved from Spain to the Americas betw

Emigration from Spain to their new world was relatively low. The estimate seems to be that only around 0.42 million people moved from Spain to the Americas between 1492 and 1820. Considering the massive amount of territory they controlled that's very low. In contrast over 1.2 million people from Great Britain emigrated to their colonies which were many times smaller geographically. Also before modern medicine and other stuff the climate outside of mountainous areas (which besides some exceptions weren't necessarily able to sustain high population density) wasn't great. e.g New England was a much nicer place to live and therefore natural population growth was relatively low. Combine those things with there being way less Native Americans in the North (due to various reasons) to begin with, very different colonial policies and treatment of the native people and the result is not that surprising.