I would like to say in addition that the system is completely ignoring what is in the `address_format` table for country Bulgaria. I tried adding states for Bulgaria and enabling the option, tried adding VAT number as a field in the address form, however, it looks like it's displaying the same form as country United States, it only says "Bulgaria" in the country drop down.
EDIT: It looks like whatever is set as "Default Country" in "International -> Localization", has an impact on the address format for user checkout - whatever the country is, it takes the format of United States
EDIT2: What fixed the problem for me in the end is disabling "Set default country from browser language" in "International -> Localization". I tried debugging but couldn't find where the problem is. For people more technically familiar with the platform, in my opinion there is a conflict somewhere between Default Country and Browser detected country and that's causing the issue.