There is the pretext for anti-immigrant activity (illegal aliens are taking your jobs!), and there is the text (foreigners with bad values are invading America!), but it is important not to forget the subtext: It is in the interest of capital to make sure we do not build international solidarity.
Comments
For the poor fools that help them, it is to find an easy scapegoat for them to blame all of their problems on so they don't have to hold themselves accountable for anything.