Hey there,
I'm just getting into NTA myself, but this was one of the main things I wanted to do, what you can do is setup a filtered view:
Use the flow navigator on the left hand side of the screen while you're under the Netflow tab
For the node: select whatever firewall you want, or a group of them if you have one, and filter endpoint by country. Once you do this if your screens don't already have it there, you can add conversations and transmitters/receiver charts to see at a glance who's doing what through which country.
For all of the views I've setup I always include country because like you said, it's a good indicator. Hope that helps!