No offense, but that's a patently false assumption which is used by the globalist elite to justify overrunning the West with third world barbarian invaders.
America's native population has continually grown, even without the help of immigration. Maybe not to the numbers it did in earlier centuries, but it has nonetheless continued to grow.
Really? What’s your source? Mine is the CDC. 2017 statistics show the Hispanic fertility rate in the US 20% higher than non-Hispanic white. Black is halfway in between. Not even Hispanics are maintaining a population-replacing level of fertility. Everyone else is even lower. I hate uncontrolled immigration and I support construction of Trump’s wall. But I’m not stupid or in denial about domestic demographics. Unless we start having more children here at home, the USA has a choice between massive immigration or economy-imploding demographic winter.
https://www.cdc.gov/nchs/data/nvsr/nvsr68/nvsr68_01-508.pdf