This mentality is generally frowned upon in the US. Aside from Native Americans, nobody has any more inherent right to live here than another; everyone either immigrated here or descends from someone who did. Thinking otherwise is seen as backwards at best. There's a Ronald Reagan quote I'm quite fond of that encapsulates the perspective:
> America represents something universal in the human spirit. I received a letter not long ago from a man who said, 'You can go to Japan to live, but you cannot become Japanese. You can go to France to live and not become a Frenchman. You can go to live in Germany or Turkey, and you won't become a German or a Turk.' But then he added, 'Anybody from any corner of the world can come to America to live and become an American.'
Who's to say which mentality is better, but, don't be surprised if you get a lot of pushback from people from the US when you talk about maintaining ethnic purity as it has only negative connotations here.
I'll start with the pushback. I'm a huge critic of my own country (USA) but that's one thing I think we get really right, and that many other countries get really wrong. I don't care what the "ethnicity" of my neighbors is. I don't give someone a blood test before I decide to be friends with them, or to welcome them into my family. This whole "I am the pure German, and you are only living here!" ethnic purity attitude is so gross and really not something I can even remotely relate to.
> America represents something universal in the human spirit. I received a letter not long ago from a man who said, 'You can go to Japan to live, but you cannot become Japanese. You can go to France to live and not become a Frenchman. You can go to live in Germany or Turkey, and you won't become a German or a Turk.' But then he added, 'Anybody from any corner of the world can come to America to live and become an American.'
Who's to say which mentality is better, but, don't be surprised if you get a lot of pushback from people from the US when you talk about maintaining ethnic purity as it has only negative connotations here.