There’s a lot of poor white people not liking poor brown people and wanting them out of the way.
I think I would want to see some compelling evidence of this before I believed it has anything to do with Trump’s popularity among poor “white” people.
For one thing, I have observed the admixture of “whites” and “brown” people. Around here, the “brown” people are mostly Mexican, although a lot of them aren’t “brown” at all. Most local Anglos and Mexicans get along just fine, and the more acclimated the latter become, the better the relationships get. Among other things, there are quite a few marriages between the two around here, although some of the older Mexicans and marriageable Mexican men resent whites who court “their” women. (notwithstanding that some of the Mexican males marry white women)
Central americans, at least around here, are much more inclined to stay within their own communities, though they get along with “whites” a lot better than they do with Mexicans.
I’ll tell you what “poor whites” (and “poor Mexicans”) resent. It’s when there are no construction jobs at all that pay decently, though they once did, and when you see a house going up, the laborers are all Hispanics who can’t speak a word of English and whose clothing was obviously not bought here, and are supervised by a bilingual Mexican who obviously picked them up on the street corners. “Legal” Hispanics can tell an illegal a mile off, much better than we can. And, at least among the “legal” Mexicans I know, they don’t appreciate those “casual labor slaves” any more than whites do.
But it might vary from place to place. It has to be realized that in much of the U.S. there have always been Hispanics. For a very long time, they were just “part of the population” and nobody thought anything about it. It has only been recently that there have been frictions. But even then, it has pretty much been a “first generation” thing arising out of self-imposed isolation. At the same time, I think “Americanization” of Mexicans has gone on for a long time too.
Again, with Central Americans, it is often different.