Really? Have you checked their visas expiration date? I don't believe you know for sure.
I know their employer, and the strict standards that are used when screening applicants. MANY of them have become Americans.
Now, you may say, how can a person be labled a Cuban, if they live in America as a citizen?
It is no different than when my grandparents immigrated. They would say they were Canadian, but had become naturalized citizens and are now Americans.