In the United States, every big city has little sectors of mini-countries, such as Chinatown in New York, Little Italy in Baltimore, and Greektown and the Arab community in and around Detroit, Michigan. These places are decorated with the decor of normal Chinese and Greek traditions, with even Chinese characters lacing every store and every single thing you see. It's basically as if you were taking a stroll through any densely-populated city in China.
These Chinese and Greek immigrants did not assimilate. They live within their own culture safely within the part of town that is their own home away from home. I cannot speak with certainty regarding how many of these non-assimilated immigrants speak English, however chances are many do not know the primary language of this country and do not even strive to learn it. I suppose that is their choice, however in my opinion, if you live off the land and call the land your home, you should have the desire to at least learn the language and "assimilate" to some minimal extent. This is not Bejing or Shanghai, but I can see why immigrants would want it to be. It's just a matter of complacency and love and necessity for the culture they have lived and breathed their entire life.
Can I blame them? I suppose not. And actually it's quite interesting taking a walk through Chinatown, experiancing the sights and sounds of a culture whose real base resides thousands of miles away. It's a pleasure to enjoy authentic Greek cuisine cooked by a Greek whose great grandfather restored the restaurant weeks after setting foot in this country...right within the confines of your own country. When you think about it, without all these mini-countries within our own borders, this place would be rather boring. And to take it to the extreme...when you think about it, the United States would not even exist.