today's immigrant isn't met by an American system that encourages, let alone demand, assimilation
This seems like an administrative issue, and an issue with yourselves. It is fully within your rights to demand and enforce these things.
immigration that was happening prior to the 90's was controlled and legal
I was maybe eight years old at the time (I've always been political), but even I remember how toxic the fights over immigration were between Gingrich and Clinton. It could not have been a new issue, it had to have roots in the 1980s. The data backs it up.
What you're missing in your analysis
Anything I wrote in a few paragraphs, will be missing crucial context. But you guys are also overlooking something. The capacity of people to fall in love with this country, over time.
15 years ago, I was one of those idiots that would go marching today in a Palestinian protest, or go and celebrate Obama's electoral victory in Harlem until 7 AM of the next day.
Now, when people visit me, I take them to Hyde Park in NY, and give them tours of the Roosevelt estate and his presidential library. If we are in DC, I take them to Mt Vernon, and give them a tour of Washington's grounds. I tell them about his years as a surveyor on the Virginia frontier, his struggles with Martha, how he set up a whiskey distillery.
I can have hour long debates about which of the Federalist essays was more impactful.
My folks and friends that visit me from abroad, tell me in disgust that I am more American than the Americans themselves.
It takes time.