Countries with Multiple World Regions
You can also have a look at the area extension (https://civicrm.org/extensions/areas)
In the area extension you can define custom areas and automaticly assign them to a contact based on his address data. 

For example if you have the area Benelux, which consists of the countries Belgium, Netherlands and Luxemburg. You configure the area Benelux to be applicable when the country of the contact is either Belgium, Netherlands or Luxemburg.

Below a screenshot of the contact card and areas for east coast and washington dc.



See the extension page for more examples.