Okay, I'll line up for the brickbats.
Latin America was settled/conquered by the Spanish and Portugese aristocracy and their wanna be's and the Catholic Church. Our East Coast was settled by English Protestants who then drove westward to settle/conquer the rest of the country, thanks to Napoleon needing cash and selling us France's claim on a third of what is now U.S.A in 1803.
The difference is cultural--aristocracy and peons on the one hand versus freemen entrepreneurs on the other. Our South was originally settled by folks who tried to bring that European aristocratic model to the U.S. but they were forcibly made to abandon that cultural model in the Civil War.
And the other part is the difference between old Catholicism and Protestantism. Catholics loved the poor, a poor man was a good even noble and holy man, and are against birth control. Protestants believed poor people were lazy or stupid, that if you worked hard, you would be rewarded, that wealth was a sign of God's favor; and they can use birth control.
There are, however, those key cultural differences you mentioned that are holding them back, and, in the modern era, those cultural differences leave them open to being ruled or swayed by radical leftists.
It's cultural ---but they can change ----instead of turning to marxism, they could turn to what made countries like the USA and Canada successful. I think the USA needs to adopt policies toward all of Latin America that promote the right kinds of changes.
I love to find posts like this one of yours. I spent some time studying Latin Ameica (more particularly South America) in college, but, you know, that only seems like yesterday. LOL. You've helped inspire me to invest some time in revisiting some of that. The whole area is likely to be so very important so very soon.