See a specialist, my guess is that as a US. citizen, you must claim your world-wide income, the US has over two hundred treaties with different governments that indicate your tax rate, if the country the income is originating from, has no treaty, it falls into the 30% tax rate. Is the income tax paid, or tax free? If you pay tax in the foreign country, you're in good shape, if not, you must pay US tax, one loophole would be if you are out of the country for 330 days or more each year, if so, you can bring in about $85K tax free.
Disclaimer, that's how I understand it, see a tax specialist that deals with foreign income.