In the form "Schedule 8812", there is a sentence, “Caution: if you file Form 2555, stop here; you cannot claim the additional child tax credit”. I think Turbotax need to update to consider this situation because some people have foreign income and they can't apply for child tax credit even if they have some kids.
TurboTax will remove the credit (and the form) once you answer the questions and qualify to exclude the income.
However, if you elect not to exclude the income and elect instead, for example, to take the foreign tax credit against your foreign income (if you pay foreign taxes), you would be eligible for the credit.
Having foreign income doesn't disallow the credit. However, excluding the income does.
Important note: If you have excluded the income in prior years and switch to the foreign tax credit, this revokes your Foreign Earned Income Exclusion Election.
Once revoked, you cannot use the exclusion again for five years without permission from the IRS. Permission requires obtaining a Private Letter Ruling (PLR), and there is a $2,000 fee to apply for a PLR. You may wish to consult a tax professional prior to revoking any election to be sure that you fully understand the implications of revoking your election.