America has a three tiered racial system: white, black, and hispanic immigrants. Of course this is simplifying quite a bit; it doesn't take account of hispanic people who aren't immigrants, doesn't deal with working class asians on the west coast or in New York City, and doesn't touch Native Americans, but I think it's generally true.
There's a quote by Jefferson Davis, the President of the Confederacy during the Civil War, from a speech he gave in the North before the Civil War started where he tried to explain the justification for slavery that sheds light on how this tiered system works. It isn't well known but it should be. Paraphrasing it, he said that because through slavery blacks did the most menial work in the society white people as a whole were elevated. He could have dinner with a mechanic, roughly a skilled worker dealing with machinery and devices of various sorts, and relate to him as an equal while if the same relationship had existed in a society where slaves weren't present there would be conflict between them. By taking the worst jobs in society, or by having your whole existence predicated on being forced to work the worst jobs in society, white skin privilege was established.
The same relationship exists today between blacks and whites, with blacks still forced to take some of the worst jobs in society due to institutional racism which has been built into the capitalist system, but there's also an element that wasn't present in the South during either slavery or most of segregation: hispanic immigrants who unlike blacks could be deported if they demanded more from their employers and whose lack of English skills made it difficult to appeal to either the government, which was racist anyways, or to groups that may have been sympathetic. The threat of deportation gives employers an advantage over workers, both legal and illegal, that wasn't possible with other groups. I say legal and illegal because being swept in raids is a possibility for all hispanic workers. But, in all honesty, I just pulled a fast one on you.
The truth of the matter is that although the rights of immigrants have been given more attention now due to the stupendous series of rallies organized by the workers themselves all over the country, it isn't like the discrimination and the tiered system just came into being yesterday. I said "in the South" because blacks are relative newcomers to both the Southwest and California. But discrimination against hispanics and the forcing of hispanics into the lowest economic register has been going on in both areas since they were seized from Mexico in the 19h century.
Hispanic agricultural workers have provided a nearly invisible subsidy for white workers since then, starting out in the areas adjacent to Mexico originally but soon spreading out over the rest of the country in areas where crops are grown.
Every group of people who are forced to work in the lowest positions of society under threat of governmental, vigilante, or institutional social consequences provides that much of a leg up for white residents of the U.S. Recognizing immigrant rights, in the same way that African American rights have, albeit imperfectly, been brought to the fore is a step towards dismantling that white privilege and constructing a truly equal society where everyone can participate.