It doesn't matter.
The checkbox doesn't impact your personal tax return. The FATCA box is a requirement for when banks issue 1099-INT forms. The checkbox isn't something that produces a result with the input of interest income. If the FATCA filing requirement box is checked, the payer is reporting on this Form 1099 to satisfy its chapter 4 account reporting requirement. If you don't have a 1099-INT in reality, it's not really relevant.
Turbo Tax includes your ability to check it, just because some people have it checked on their actual forms. It doesn't actually produce a result in Turbo Tax. So, it really doesn't matter if you check this box. It matters that you report your interest and file your FBar.
When you file your FBar (separately from Turbo Tax), you will obviously list your foreign accounts. No information is communicated to the IRS by your checking (or not) of this box inside Turbo Tax.
