Why does Turbotax ignore foreign tax paid on interest income when calculating the credit?

Are you saying that you are receiving Review errors and the foreign tax credit is not yet calculating?

Or are you saying that you are receiving no Review errors and the foreign tax credit being calculated is not a satisfactory amount?

If so, the computation of the credit, by its nature, is limiting.

IRS Publication 514, page 18, states:

Limit on the Credit 

Your foreign tax credit cannot be more than your total U.S. tax liability multiplied by a fraction. The numerator of the fraction is your taxable income from sources outside the United States. The denominator is your total taxable income from U.S. and foreign sources.