Ok, so it's not a theory. It's a fact. Repeated over and over again. The American population has been replaced since, oh, 1492. With significant bumps in 1619, and then centuries later in 1965 with the change in immigration laws. Who cares? Replacements bring better food, better music, new holidays, etc. Without replacements, there would be no Sinatra, Bennett, and Dion, no pizza and piñatas, no tacos. Imagine America without tacos! Of course Mexicans in the southwest complained about Davy Crockett and other gringo replacers, who replaced tacos with boring sandwiches. And no St. Pat's day, no green beer, and no Jimmy Cagney. Watch "Yankee Doodle Dandy" and then think of America without Jimmy Cagney. And tell me, how would we have survived the 20th century without Jewish comedians?