The population of the US is now more diverse than it's ever been. Mere fact. Whites will likely become a minority like all the rest in another 25-30 years. More fact.
We can embrace that, say it's a good thing, or we can whine about it as if we're actually losing anything in the process. To claim that we might be is fundamentally racist. Part of it is that immigrants have more children because they're optimists who see a bright future in this country & aren't steeped in the inherent negativity of the right wing.
There has always been a faction of xenophobic mow-rons in this country. Quakers were shunned by Puritans. Germans & Dutch who settled Pennsylvania were widely hated. Then there were the Irish, The Mennonites, the Swedes, the Italians, the Jews, Poles, Serbians, Chinese, Latinos of California & the Southwest plus all the rest.
Guess what? We swallowed them up & added their distinctiveness to our own, remade ourselves in the process. It's how we roll. We're like the Borg except it's all voluntary. You will be assimilated. We'll change some in the process just like we always have & emerge stronger than before despite the nay-saying & fear mongering.