The NYT had an excellent piece on how a variety of arcane restrictions make it difficult for even well-trained foreign physicians to practice medicine in the United States. These restrictions are kept in place at the insistence of the doctors' lobbies since they allow them to sustain their high wages. This is a great example of how Washington is dominated by protectionists who are intent on using trade barriers to protect special interests even though it poses enormous costs on patients and the economy.
It is worth noting that one of the issues raised in the piece, the potential drain of educated workers from the developing world, could be easily remedied. Since doctors must be licensed to practice, it would be a simple matter to impose a modest tax on the income of foreign trained physicians (e.g. 10 percent). This tax could then be repatriated to the home country so that it could train two or three physicians for everyone that came to the United States. This one is so simple that even an economist could figure it out. In this way, the sending country would benefit as well from the decision of their doctors to immigrate to the United States.