1. Get an additional list of more countries here: http://www.ubercart.org/project/fullcountrylist
2. Unzip the files, find the ones you would like to add and upload them to the server at this path: /sites/all/modules/ubercart/uc_store/countries ; you should see plenty more .cif files there.
3. Log into your Drupal administration panel and select:
Administer > Store Admin > Configuration > Country Settings and select each country .cif file
brought to you by 20 Miles North Web Design and Hosting