Ive worked beside many IT workers who worked from 1 to 10 years in Japan on Japanese style “green cards”. Your information on Japan is incomplete. Japan is not as open-borders as we are. But it is far from a closed society.
One key factor is that many immigrants know some English before coming to the US as US English entertainment is worldwide and spreads the language. And on the flip side, there are large foreign language communities in the US. So a Pole, Russian, Hispanic or Brazilian who knows little English can easily find others with whom he can communicate.
I’ve often ordered from fast food workers who didn’t know English and I had to place my order in Spanish. No problem. It’s a free country. :)
But, whatever Japan has...it is done legally!!!! That’s my main point.