The right wing populist are only using illegal immigrants as a venting tool for the working class of America, if the Democrats and the old GOP wants to do soemthing about Trump and his politics; it's tiem to take a hard look in the mirror.
Inequality is extreme in America, Social Mobility very low, the American Dream is dead for the working class, Democracy suffering under lobbyism and money currents. Back in the day hard work was the creator of dreams, not so much anymore (despite so numbnuts still believing it); education, controlled immigration, and increased equality are tools to handle populism. Oh and reform the political and financial systems - 'Trickle down economics' is a trick, only the rich gets richer.
Globalism have benefitted the few, not the many and in this "truth" lies the answer to Trumps success and the Democrats blind spot. Populism is a fundamental criticism of the existing system, so voters will vote for whomever wants to change the system, despite him being a complete asshole.