Pizza,
It was Blacks and Puerto Ricans that brought older White ethnic communities together in New York. In both cases, the new residents didn't technically qualify as immigrants..because the Blacks were coming from rural South and PRs are citizens. Throw some West Indians and Dominicans in there also, but mainly American Blacks and Latinos.
I bring the distinction about them not being immigrants because as non immigrants....they don't go through the vetting/screening process that actual immigrants go through to get here. Normally, because of that screening process....some of the most determined, resourceful, and motivated people are allowed to come here. Regardless of what social strata of their homeland they are from, they have the tools to thrive here.
The Americans migrating from one region to the other(rural south or PR to New York) don't go through that process, so while many of them are determined,motivated and resourceful and will succeed...the ne'er do wells aren't weeded out.
The behavior of the new groups brought the White ethnic groups together as they realized that they shared some core values that they didn't see in the newly arrived groups.Also after a generation..people were no longer of mother country nationality, but Americans of this or that background so kids went to school and dated each other and eventually marry.Even just between Irish, none of the animosity and hostility which exists back home along religious lines carries over here.
People blend into the proverbial melting pots.
I've always said and believed that New York hyphen Americans are more advanced and evolved than their fellow countrymen who landed in different parts of the country or even the region. Faster paced life and more mingling of different people in New York.
In a lot of parts of Jersey, the different White hyphen Americans are still at each other's throats...and there are towns and sections of towns that are exclusively (insert country of origin). On several occasions..in social outings... I've had White people tell me straight up how they HATE another White ethnic group. First time it happened, I'm thinking wow...what do I say?...and if he feels this way about other Whites..I'd better get the F out of here before they start burning crosses.
Whites shitting on other Whites in front of Black guy let's you know that they REALLY don't like the other group.
It's happened enough that I know how to react. I use the classic Seinfeld line and it always gets me off the hook "Yeah, and don't get me started about the Blacks and the Jews". They get the reference,they laugh and change the subject. When the Bridge Gate story broke and the Christie guy's email read "time for trouble for that little Serb"...that's typical Jersey stuff.