This is the real immigration problem. When we had nearly unchecked immigration during the first 30 or so years of last century, the country wasn't a welfare state. The immigrants worked or they starved - most worked, but admittedly some turned to crime. All in all, that immigration boom was a benefit to the country.
Plus, there was a large "salt water guillotine" (as George Will puts it) that forced the Italians, the French, The Polish, the Irish etc. etc to assimilate. Now, with the acceptance of the Spanish language, the ubiquity of Spanish entertainment options and cheap and abundant travel back to their home country, the Latinos even in the second generation are not assimilating.
Although I'm not entirely pleased with some of the racial overtones of this debate, it's silly to think that the flood of immigrants under current conditions won't cause lasting harm to the Republic.
I grew up in an immigrant neighborhood and am married to an immigrant. My grandmother was an immigrant. The problem is that the numbers today are so large, we can’t assimilate them. And since they are mostly Hispanic, a critical mass is being reached where the immigrants are demanding that we accommodate our culture, language, etc. to their’s instead of the other way around. And there is also the political dimension since 87% of the 1.2 million legal immigrants who enter annually are minorities, as defined by the USG. Immigrants and minorities vote predominantly Democrat.