Only if you're the sort of person who cares about such things. I don't see any moral imperative to make sure any particular ethnicity or culture continues.
Before someone calls me the usual assortment of bad things, please take a moment to consider (1) the difference between treating existing people well and making new people, and (2) that I mean this literally and not in the "all the cultures besides the US should go away" sense, and would still take this position even in the blatantly racist "but that means you'd be a minority" situation you're about to try to catch me with.