But obviously if you came to work in the US, you are subject to their taxes. But and once they leave and all taxes are resolved, they should not be subject to it any further.
That is obvious, the thing is that in America a "permanent resident" and "permanent resident for tax purposes" are two different things, and IRS does bestow the second status quite liberally, and once you are deemed a tax resident, it is hard to get rid of that status even long after you left the coutry.
