If you are in the same boat as me, please to a POST request to https://www.roblox.com/account/settings/account-country with the param of countryId: XXX replcacing XXX with the country code of the country you want, endpoint gives all of them in a JSON object if you do a GET request.
Did I have to find an archived version of the website to find this API endpoint? Yes. Prob shouldn’t have been that hard.
It says in the dialog that it can only be changed once, not once every 365 days. After changing on a alt it becomes permanently locked and text is displayed under saying “Contact Roblox Support to change your Account Location”. Is this intended?