...but according to ServiceNow (OTB) there are only 9 countries in a suggestion field. Now I work for a global organisation and with offices in 30+ countries and staff who travel to many more. (We capture travel in ServiceNow.) So here is a quick and simple enhancement that we implemented to add 205 countries and their ISO and dial codes, so that we could reuse them across our instance

1. Create a u_country table (extend the Task table)
2. On that new table create these fields: Name, ISO Code, Continent, Dialing Code, Idd Prefix, Ndd Prefix (type string)
3. Download and import [asset|aid=1179|format=link|formatter=asset|title= 205 Countries and related data from here.]
   (the attached list also contains additional locations that have alternate dialing codes)
4. Use your new u_country reference field across your instance. Obviously you could add all sorts of other data to this table that might be useful to your organisation.

Hope this helps!