> This single statement, monstrously ahistorical as it is, allowed me to dismiss everything else you're saying because this narrative emerged only recently, around 2014 or so.
Oh? Which part of this is wrong? All of it, or just parts here and there?
Mexican territory -> Anglo-American settlement (I can draw comparisons between this and Israeli settlements in occupied territories even if specifics are different) -> rebellion against Mexico -> independent Republic of Texas -> U.S. annexation -> US vs. Mexico war, where the USA got at least as far as Mexico city due to Mexico having negligible capacity for self-defence -> Mexican recognition of the new U.S.-Mexico border.
> Are you going to tell them that this isn't a good "standard" of civilization?
I'm in the set "them". I looked at you, the USA, from the outside more than once, and my decision every time was "you know what? I don't need any of that nonsense". Likewise for many of my peers, at least one of whom resigned from a big tech firm rather than be relocated to the USA.
Guess what: a lot of nations have the "we are the best, everyone wants to move here" narrative. That includes the UK, which I infer from your use of "here" to refer to the USA, is a place you do not live and are unlikely to want to live in.