Bullsh*t,
Inbreeding leads to weakness of a species. The melting pot of Americanism is where people from all over the world assimilate into what is purely American history, values, and ideals. Bring them in from all over the world, orderly and fully committed to those ideals. If they want to adhere to Chinese ideas…go to China….and so on. Multiculturalism seeks to divide, denigrate, and Balkanize. That is not the American Way. But, it is where Progressivism leads.
In agriculture, the practice of growing the same crop each year leads to increased pestilence and disease. That’s why farmers are advised to rotate their crops. Human culture is analogous.