I wonder what would happen if a dual Polish-American answered that question "no", since according to Polish law, those Polish citizens born in the U.S. are considered to be only Polish citizens.
The bank would be entitled to recover any losses as a result of the fraudulent declaration.
If the bank had a problem and tried to sue, the courts should return a verdict against the bank, since only Polish citizenship is recognized in Poland.
It doesn't work like that. The "recognition" comes from the fact that you must identify yourself as Polish to the Polish authorities should they wish you to confirm your identity. The question asks clearly if you're an American citizen - and financial fraud is serious here.
Anything else would be clearly discrimination.
Good luck arguing that one when you're hauled up for fraud in front of the Polish courts.
The issue is how Polish courts address the issue, which should be according to Polish law unless Poland has again become someone's puppet state.
Polish law requires you to follow the requirements of FACTA irrespective of being a Polish citizen or not.
Again, if our hypothetical Polonia investor wants to invest without the Americans finding out, renouncing American citizenship is how it's done.