I don’t know if that’s sarcastic, but banks are scared to hell to deal with US citizens. They won’t ask you to fill the other box, they just won’t deal with you.
It is not sarcastic - my bank (ING) has these in the forms, for instance when getting started with their stock buying program.
Many banks will not allow US citizens to open accounts for that reason. If they have any US account holders, they will have to report to their tax authority.