A US citizen is taxed on worldwide income which would include income from trading securities.  the exception for you being the foreign earned income which can be excluded if you meet the tests,  investment income is not earned income.    it is possible that your resident country would also tax the investment income.  if so you would get some sort of foreign tax credit on your US return for the income that is taxed by both countries.   Your address should have no effect.  TT should have a section in the tax info worksheet to enter a foreign address.