Associate state and country fields when not tied to a particular address type
If I understand your question correctly, I may have just posted an answer to a similar question I had.  Hope it helps you.

https://civicrm.stackexchange.com/a/18093/2169

In summary, it's to use the civicrm_buildForm hook in order to tie your country and state fields together.  That will cause the states' list to be refreshed when you choose a country.