Note that this is only looking at legal immigration. Pew has previously estimated that there are also about 11.1 million unauthorized immigrants in the United States, and the overwhelming majority of those come from Latin America and the Caribbean.
That said, legal immigration still makes up the biggest chunk of the foreign-born population in the United States — and it's growing more rapidly. Of the 43 million foreign-born residents in the country, about three-quarters are here legally. And over the past two decades, Pew notes, the United States has added an average of 1 million legal residents per year.
Meanwhile, the pace of illegal immigration appears to have slowed down since 2007, although it's still not entirely clear whether that's due to better enforcement or temporary factors like the weak economy. “The best estimate available to date,” argued a recent Council on Foreign Relations report, “is that enforcement increases explain approximately one-third of the recent reduction in the flow of undocumented migrants, and economic factors the remainder.”
--Here's an even longer view from NPR. Back in 1960, three-quarters of the foreign-born population was from Europe and just 1.5 percent was from Latin America.
By 2010, that had shifted dramatically, with a quarter of the foreign-born population from Latin America and just 12.3 percent from Europe.