They have been discussed for years In America with the same calls that America was being overrun.
First it was the Germans, then the Irish, then the Italians, then the Poles, then the Jews, and now people from Latin America.
History is not on your side about your concern. Your concern has been proven wrong in the last 225 years.
The Mexicans, Puerto Ricans and Central Americans, etc. coming to the U.S. push for the adoption of THEIR language as an offical tongue in the United States, equal with english. They violate U.S. laws consistently (arriving illegally, avoiding taxation, committing crime at an astronomical rate compared to whites). The Arab/Muslim immigrants plan to turn the U.S. into an Islamic state. Hey OK!- so only 40% of them are thumbs up on that one- that's a problem in my eyes. The Chinese are from a nation with which we will probably be in a shooting war within 20 years.
While history is full of Cassandra-like pronouncements of doom, it is also full of Ostrich-head-in-the-sand acts that make plain truths staring one in the face invisible.
Lastly, I'd like to know if some of you believe that there is an active agenda to make America a non-white nation, or are intersecting priorities (cheap labor/low wages, need to grow the captive consumer markets, desired influx of Democratic-voting immigrants) simply making use of whatever human material is needed to bring these about, and that the current available humans to implement these goals are non-white people.