In my country, and I assume in the US, immigrants are useful to the bourgeoisie as highly-vulnerable and highly-exploitable labor. As many say, they do the hard and dirty jobs which other people don't want to do, they can be coerced with threats of deportation. And with the US Republican Party's apparent attempts to reduce offshoring and bring production back onshore, surely powerful sections of the bourgeoisie have an interest in lowering labor costs to compensate.
A popular answer from the mainstream is to simply point to White nationalism and other bigotry. Another answer is that illegal immigrants acts as a scapegoat and a way for their party to signal to citizens that they're doing something to solve their problems. And while I think these are reasonable and plausible suggestions, I want to explore other options before assuming a simple cultural explanation. For example, liberal media tends to frame Middle-Eastern conflict with the Zionist Regime (and even Western support for the regime) as religious conflict or even a racial conflict, rather than colonial imperialism.
I do think the scapegoat narrative is plausible, when people have somebody "lower" than them that they can hate and look down upon they stop looking up for answers to their suffering.
The modern political and social machine is more complex than one single agenda, there is no secret entity deciding everything for everyone, though in America the 24hr news broadcasts like Fox and CNN are awfully close to being exactly that. Rupert murdoch and his ilk are definitely master sociologists, and perhaps the outrage benefits them personally.
Humans are terribly exploitable, both from a labor and rights perspective as well as a puny meat brain will believe what you tell it perspective.
Monkey mad that other monkey come and take all banana. It's an easy narrative to accept instead of addressing the complex and corrupt distribution of wealth.
In my area, the loudest about immigrants often exploit those same immigrants for work on their homes. I saw a guy with a "close the border we're full" sign on his home using some spanish-only speaking immigrants to paint his house, no doubt for cheap. They literally had to paint around the sign demonizing them.