I thought this was well-known, at least broadly-speaking.
But I don't read much into it. America's ideal of mass immigration without regard to race was an evolution.
It's a noble ideal. A triumph of hope and American even-handedness.
On the other hand, it's generally a mistake to judge the past according to current ideals. It's way better to apply contemporary standards to the politics of any particular time. That way, you discover how they thought.
Nor is it obvious that the current ideal is working well today, Perhaps the pot doesn't melt in the way it was hoped it would.