If your friend emigrates, they may put a burden on the country they go to. Even if they are productive, the cost of their ailment (assuming its not just ridiculously ovepriced medicine in the US that is in reality really cheap everywhere else, in which case the nation he immigrates to should be overjoyed at the opportunity!) can slow economic growth over if someone with no ailment and the same qualifications emigrated instead.
So the US "sheds" a "cost center" and another country takes on the burden. American companies keep turning over record profits and stock valuations while its poor and sick suffer and die, while other nations are burdened with those America should have taken care of itself with its vast wealth if only it had any morality to care about its citizens.
Just this week, a friend who is middle class with chronic but manageable health problems was expressing serious intent on leaving the U.S. precisely because of long-term bankruptcy from medical cost prospects.