There were plenty of neighborhoods in New York in the 1910s, 1920s, 1930s, and 1940s that were strictly defined along ethnic lines -- if you were Irish you knew to stay out of the Italian neighborhoods if you knew what was good for you, if you were Polish you avoided the Hungarians, if you were Jewish you avoided the Irish, and so on and on. You could spin the radio dial in the years before WWII and hear a Tower of Babel's worth of different languages -- Yiddish, German, Polish, Hungarian, Italian, Lithuanian, you name it. And meanwhile "race suicide" crackpots wrote long, hand-wringing articles in the Saturday Evening Post about how all these unassimilable immigrants were going to be the death, oh, the utter DEATH of God's Own Country.
And yet somehow, the world spun on and the children of those immigrants grew up to become splenetic senior citizens -- whose own "whiteness" doesn't extend back more than a century as such things were once understood -- fulminating about what all these new Others will do to God's Own Country. It's an old song, just one with a new arrangement.