The answer from TurboTax is correct in most cases. Enter '0' for line 6 D (2017) or 7 D (2018). If you are trying to deduct Foreign Taxes paid using Form 1116 often this is because you had a mutual fund that invest in foreign stocks however per Vanguard 1099 small print,
"U.S. mutual funds that invest in foreign securities may elect to pass certain foreign taxes paid by the fund on to their shareholders on IRS Form 1099-DIV; however, because the funds are U.S. corporations, the dividends paid by the funds are considered U.S. source dividends."
Thus '0' is the correct answer!
