There are a great many accomplished, upstanding US citizens of Irish descent today, but let's not forget that mass Irish immigration also brought machine politics & race riots to the USA in the short-to-medium term.

"Underclass" isn't meant as a moral judgment, I'm just talking about the people who work low-wage, low-prestige jobs with little job security. The USA already has fairly bad ethnic stratification of income; I don't want us to turn into Brazil or Mexico in that regard.

As a moral or practical matter, I don't think deporting families is a good idea. I do think we have to find a way to stop digging a hole. Let the people who are here now assimilate - it's harder now, with modern communication and transportation technology, because it's so much easier to live in an enclave. Find ways to encourage people who are already here to have more kids if there is a concern about future workers.