It's also a sign of national balkanization.
Is it?
Was America balkanized when German immigrants refused to learn English... instead settling entire towns where German was the only spoken language?
Was America balkanized when the Chinese came and built our railroads, settling in Chinatowns where they didn't need to learn English?
The German-language towns only started to use English with the start of WWI... and we can still visit the Chinatowns in New York, LA, and San Francisco.
I find it exceedingly strange that the arguments used today apply to our immigrants of the past... yet the prognostications never came to pass. What makes today different?