It’s a combination of books, news sources, and some formal education. I was lucky that my highschool still heavily invested in humanities before I went off to a stupid ass tech collage. Beyond that I am constantly researching things because I’m weird. So when people pull up reasons that are fairly well documented quite literally easily sourced on wikipedia of all places it’s incredibly easy for me to remember and reference them.
This doesn’t change anything. Since AMLO the Mexico itself has acted as the US southern border and worked to prevent caravans from making it to the US.
This is just Sheinbaum mystifying the position of Mexico