America growing and prospering has been working just fine...if you hop on a plane and revisit CA and the rest of the West Coast, you'll find that immigrants speaking over 100 languages are assimilating just fine...case in point...our second generation Vietnamese owned car repair center is constantly flooded with cars from all over the area, and when you call them on the phone you wouldn't know they came from another country...they sound, talk and act just like folks whose families have been here for a hundred years.
America was built on Immigration...ALL of us are descendants of Immigrants...it's in our national DNA...unlike European and most other long established countries...they are very much 'Insular'...and therefore less welcoming to 'outsiders'...just like Japan and China.