That login bug could be what started this whole mess. or maybe not. You can change the login screen to NA by adding /login?locale=na
(ex https://membership.square-enix.com/sqex/login?locale=na) at the end of the string. Not sure if its even in use though because it doesn't have a flag icon like the other ones do.

changed it to na and processed my code and got the same eu code. in fact I went to just about all other languages and tried it and i got the same code. It looks like it doesn't even try to process it, it just checks if its already been submitted and if that returns true then it just gives you the same exact code.