I think you need to report in any case, the $10,000 might be a threshold below which the bank does not inform you to the USA. The real threshold below which the bank needs to look at you is $50,000, or if you have stocks, funds, or investment-grade products, such as some insurances, $0, but some banks are using a lower threshold. Also do note that this is for preexisting accounts - new accounts need to be looked at and can end up being reported irrespective of the amount they hold.