That's OK. We have more than enough replacement population walking in across the southern border.
The nations population continues to grow rapidly. An absolute impossibility with 1.86 births per woman of child-bearing age. But not impossible with massive immigration, documented or undocumented. Per US Government statistics, in 35 years the white race will be in the minority, with 47% of the population being white in 2050. I'm pretty sure that I've read that for the case of children age 8 and younger white minority status is already the official reality.
If current trends continue, the population of the United States will rise to 438 million in 2050, up from 318 million in 2014, and 82% of the increase will be due to immigrants and their U.S.-born descendants, according to projections developed by the Pew Research Center.