I doubt very much that will happen. But the question is, if that did happened, would the United States still exist? That population increase can only come from immigration. While some immigration can help a country, massive immigration while there is a demographic collapse is not going to help. It just means the new owners of the land are moving in. Like Rome, like the Mayans. The Toltecs moved into the Mayan cities as they were collapsing. The Germans moved into Rome.
Immigrants Will Form Half of Russian Federation’s Population in 2050, Experts Say
I guess that's one reason to go looking for extra Russians in Ukraine.