March of the Non-White Babies

By 2050, there will be no racial majority in the United States. "Minorities"—or groups that are thought of as minorities now—will outnumber the white population ...

The share of so-called "new minorities"—Hispanics, Asians and multi-racial groups in America—is going to double. If your first guess is that this is all due to immigration, you're not entirely wrong—it's because of past immigration. What's really driving the growth now (and will continue to do so in the future) is that majority of the immigrants who are already here are at the baby-making age ...

This is good news, demographically speaking, because as it turns out, the white population in the U.S. is aging pretty rapidly. This surge in minority births will arrive just in time to pick up the slack, Frey says. Absent any major change in immigration policy, the future of the American labor market will depend on the next generation of U.S.-born minorities ...

It's kind of a zero-sum population shift for whites. [The white population] isn't growing very rapidly at all. That means any place that gains whites through migration means some other place has to lose them ...

CAIRCO notes

In 1972, American women voluntarily reached replacement level fertility (2.1 children per woman). Population momentum (where today's children grow up to have children of their own while their parents are still alive) would have driven native-born US population to increase for several decades, then slowly decline to a sustainable number. 

Yet mass immigration is driving US population to double within the lifetimes of children born today.

For more information, see Population Driven to Double by Mass Immigration.