Inform creators that Direct Deposit is not available outside US
Twitch should inform users who are adding or updating their payout method that Direct Deposit is not available for anyone outside the US.
While filling out your payment information, it asks you to input what country you are from. If you enter a country outside of US, and try to select 'direct deposit' as your payment method, there should be some mechanism there to stop you from moving forward, or at the very least, a notice somewhere on the page that direct deposit is not available outside the US. This would prevent someone outside the US from inputting their bank details and having their payment fail.
In addition, if the payment fails (especially due to being outside the US), include in the email noticing of this, that being outside the US is a possible reason for the payment failing.
Additionally, there should be information on the 'Rejected Payouts FAQ' website that direct deposit will not work outside the US, since this is no where to be found.
There is nothing preventing someone from outside the US selecting direct deposit as an option, and nothing informing them of why the payment fails when it does, despite direct deposits only being available for US residents.