This is a common problem for people who use apps that are limited to particular countries. BofA's IT folks, for example, never imagined that anyone outside the USA might ever be a BofA customer, so they listed their app only on the US Apple Store.
The only workaround I know of is to maintain a separate Apple ID in each country for which this is a problem. For apps like BofA, this is no problem.
From a PC (not your iPhone), create a new Apple ID with a new iCloud.com email address using your US mailing address. Don't register a payment method. Then, from your iPhone, log out of your current Apple Store ID and log in with your US Apple ID. Now, you can download the BofA app and install it -- and use it. Log out of your US ID and log in again with your regular ID.
All will be well until BofA offers an update. You will get the update notification, but you will again need to log in to your US ID in order to pick up that update.
Good luck.