Hi,
I think that you'll probably find some answer through this
thread
:
You must have either a javascript error on your website or you had edited one of the of the views of the registration area and because of that you didn't get the modifications for the new country/state system in 2.0
So you should first check your browser javascript error log for that page to see if you have any error. And check that you didn't edited one of the files of the view "user" or the file "login" of the view "checkout" via the menu Display->Views.