Politically Incorrect, that is...
There's only one nation that survived unfettered immigration.
There's just no other way to describe the process that two waves of Irish and Italians were subjected to to make Americans of them.
Since Irish and Italians are white, perhaps it's not racism per se. And the first wave of Irish who'd been assimilated heartily participated in the process of the second wave.
But the treatment forced the children and grand children of Micks and Wops to become Americans to gain access to the full American dream.
The shitty little ghettos weren't allowed to grow to become enclaves.
Yes, you could live your entire life in a "Little Italy" and never know the world surrounding it. Some did. But you couldn't leave without either having a damn good reason, or being able to blend among the natives.
It's not a pretty process. It's extremely harsh. It's got massive flaws where skin color announces the origins (but we always forget that, before LBJ, our darker toned people had very nearly pulled it off. You may thank the War On Poverty for ruining that!). Chinese immigrants DID pull it off! Mexican immigrants pulled it off for decades, nearly a century, before we decided that unfettered diversity was better than assimilation.
It was understood that if you were to move to America you'd be expected to become an American or have a very hard time of it. And we made Americans, by the literal ship-load.
Somewhere along the line the process was replaced with hate for hate's sake. Again we can thank the Democrats for fucking it up.
I marvel at the make-up of the 1930's America. Yes, there were black neighborhoods and that's where blacks were expected to live; yet the houses were the same as everyone else. You could not tell a white neighborhood apart from a black one without seeing the people who lived there.