This is why, of all the schools I've gone to, LA City College remains the hardest, even after later graduating from a top ten engineering school. I was originally a biology major, and with Los Angeles flooded with refugees and immigrants, a whole lot of medical doctors and research scientists from former Soviet republics found themselves in a country where their licenses and degrees were not accepted, and they had to start over. Many of them ended up totally obliterating the curves in all of the underclass bio courses in various Los Angeles community colleges.
If really really smart immigrants stop coming to America, the country will be in deep shit, IMO. Per your question: they don't have to be from Soviet countries, just with qualifications that aren't accepted at face value.
