The Northern Virginia doctor knows at least that much about his situation. He knows he is no longer considered a citizen of the United States — the place where he was born, went to school and has practiced medicine for more than 30 years — and that he also belongs to no other place.
A letter from a State Department official informed him that he should not have been granted citizenship at the time of his birth because his father was a diplomat with the Embassy of Iran. The letter directed Sobhani to a website where he could apply for lawful permanent residence.
Paying taxes has nothing to do with citizenship, but with residency. You can be a non-resident (for many years) for immigration purposes, but you are a resident for tax purposes after about one year in the US. Even illegal immigrants often pay taxes on earnings, using an Individual Taxpayer ID # (ITIN). It is true that the US is one of the few countries in the world that mandates its citizens and Legal Permanent Residents, no matter where they live, no matter where they earn, to file taxes. A number of those will have to pay additional taxes on that income to the IRS. Taxes taken to a foreign tax authority can be subtracted.