Veteran immigration enthusiast Ben Wattenberg is being optimistic about America's population in the Wall Street Journal—America's 21st-Century Population Edge | Birth rates are dropping all over the world, often below replacement rates. But not in the U.S. May 23, 2012.

He writes 

Look around you. For most nations of the world, birth and fertility rates have never fallen so far, so fast, so long, so surprisingly, all across the globe. Except for America.

Seen globally, the population explosion—or what Stanford's Paul Ehrlich called "the population bomb" in the 1960s—is now stone-cold dead. The ramifications are enormous economically, geopolitically, culturally and personally. For one, the United States will become stronger than ever in the games nations play.

Every other major modern nation and every developing country has low or falling birth rates. Japan and Poland see 1.3 children per woman, Brazil and China 1.9, Pakistan 3.6 (down from 6.6 three decades ago). American fertility rates are relatively high, at nearly 2.1.

Having children is an affirmative act, so it's little surprise that surveys—Gallup, Harris and others—show Americans to be the most optimistic nation in the world. (Israel, too, is an optimistic nation with a sense of mission and high birth rates.)

Then there's the effect of immigration. According to the United Nations and the U.S. Census Bureau, the U.S. takes in more immigrants than the rest of the world combined. Think Albert Einstein, Madeleine Albright, Andy Grove, Albert Pujols, Sergei Brin, I.M. Pei or David Hockney.

Drive in the suburbs and exurbs of many major American cities and you will see McMansion homes with three, four or even five children—McPlenty—unheard of anywhere else. American couples can choose to have many children because the U.S. is one of the world's few suburban nations. In suburban settings, some affluent parents are deciding that for a decade or so raising a large family is more important than having two earners.

All this and more yields an America that is projected to have 400 million people in 2050, up from 310 million today and possibly on the way to 500 million by 2100. This may not quite play out—immigration from Mexico will likely fall as Mexican fertility drops off—but the trend lines are far stronger in the U.S. than elsewhere. [More]

 

Yes, we've heard about the demographic death spiral, and how Russia is running out of babies, and it would be nice to think that Americans are doing a better job of reproducing themselves, but the people who are reproducing themselves best in the United States are not necessarily American. That's why there were more non-white than white babies born in the last Census Report, and why America is expected to be a white minority nation by 2050.

And please don't tell me about Einstein—immigrants today aren't Einstein.

In The Bell Curve  1994, Herrnstein and Murray wrote 

The rules that currently govern immigration provide the other major source of dysgenic pressure. It appears that the mean I.Q. of immigrants in the 1980s works out to about 95. . The low I.Q. may not be a problem; in the past, immigrants have sometimes shown large increases on such measures. But other evidence indicates that the self-selection process that used to attract the classic American immigrant—brave, hard working, imaginative, self-starting, and often high I.Q.—has been changing, and with it the nature of some of the immigrant population. [p341, quoted at some length here]

Of course, this is something you're not supposed to notice. Peter Brimelow wrote in 2000 that 

The original draft of my huge 1992 National Review cover story "Time to Rethink Immigration" contained a discussion of IQ and immigration policy, alluding to Richard J. Herrnstein's and Charles Murray's book  The Bell Curve   which I knew was in preparation. The reaction of my dear friend John O'Sullivan, NR's Editor in those happy days, was very instructive. Not only did he insist on cutting out the discussion, but he also hunted down every copy of the original draft in NR's office and had them destroyed. His argument was that any mention of IQ or heredity at all would result in the issue monopolizing all response to my article, plunging the rest of my very broad case against contemporary immigration policy irretrievably into the dark. No doubt he was right. But public debate on both immigration policy and the IQ issue has gone backwards since 1992, although the issues are more pressing than ever.

So it has.

All the immigrants mentioned in Wattenberg's laundry list are white, except possibly Albert Pujols, the Dominican first baseman, who's slightly tan. (Although this may be because he's outdoors a lot.)

The United States is not going to outperform China with the aid of Mexican peasants or African refugees.