system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: Why is Mexico so poor compared to the US and Canada?

They all were settled at similar times. Is it due to the Spanish taking out all of the gold? Does it stem from their loss in the Mexican-American War? Is there a more recent cause?
gpt
Canada and the USA were settled by parceling out land and by bringing excess labor from abroad (Europe, Africa, etc.  Mainly Europe though) to develop the land.  So this lower population density allows for a more equitable distribution of land.  This also affects the way the colonists are treated by the governments that were set up.  

Mexico and South America had the larger native populations and the system for settling was not to develop and make life better for colonists, but instead to extract wealth and labor to Spain. The majority of the labor was done by natives and when they died off Africans were brought in massive numbers.  This method of colonization also set up governments that were more oppressive for the people of Mexico since Spain didn't view Creoles as highly as England saw USA and Canadian colonies.  

Another important aspect is the environment.  Jungles, deserts and mountains are a lot harder to develop. Those are the main habitats in Mexico and the rest of the Americas.  

These reasons are more of roots,  but there's plenty more reasons that require more reading and can't he Eli as easily.