The Anglo-American settlers involved in the Texas land grab, as well as the Mexican War and other annexations and ripoffs that followed, were little concerned about depopulated territories and corrupt Mexican Hidalgos. It was simply a case of invited guests who decided to move in and never leave.

Perhaps other motivations included expanding the American slave economy when their own country was being increasingly dominated by Abolitionist sympathies. It was the slaves who really "payed the price".

I just watched the Disney film about Davy Crockett's heroic last stand at the Alamo. I'm not surprised that the role expanding slave territories played in "Manifest Destiny" wasn't brought up there either. History is written by the winners.

As for Puerto Rico, I lived there for a year, back in the 70s, working as an undercover colonial official (without portfolio). I've already bored everyone here innumerable times with that story.