That is the problem with having a flood of people from the country next door and not from overseas.
They used to have to be cleared in NY after crossing in ships and it was tough to get back at all. That IMO made them loyal to their new country over the old one.
The exact opposite is true of Mexicans and why they still consider Mexico #1, though it is one big #2 IMO.
George Will nicely phrased it - the immigrants were "pyschologically guillotined". After they arrived they could get by with native language newspapers and enclaves but by the third and fourth, if not the second generation, their families had integrated and become Americans. I knew many an immigrant family, even as late as the '40s (yeah, I'm THAT old) where gramps spoke only the old country language, his kids were bi-lingual, and their kids spoke only English. As per the poll, these newbies don't want to become Americans, just live like them.
There was also an deep appreciation of the opportunites here compared with the Old Country. I worked with a Russian Jew who, one day, showed me his property tax bill. I thought he was bitching about the amount (this was California) and I agreed that it was high. he said, "What are you talking about? In my country I couldn't even OWN property. Now I am a Land Owner!"