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.
What's strange is that there isn't an oversupply of labor, and in fact, they're slowing economic growth with the downward pressure they're putting on the labor supply. Slowing economic activity certainly lowers wages, but it lowers profits too. Perhaps this is temporary, and once labor has been properly disciplined they'll quietly reduce the number of deportations, but at the rates they're going they're going to leave produce rotting in fields and construction projects unfinished.
Maybe it's to increase pressure on states to lower work-age requirements and loosen regulations on child labor? We're seeing that happen in some states already, and as the superexploited migrant labor force shrinks it'll force more-and-more states to start putting children to work in the fields, factories, and construction sites.