For those struggling with the ability to change the country code of a remote antenna. The following works for me on NanoStation M5s, Rocket M5s, and PowerBridge M5s.
1. Ensure that I can log into the web gui, and go to the wireless tab.
2. Open my putty program (download at putty.org)
3. SSH into the IP of the antenna and log in using the same credintials as the web gui.
4. Type the following: vi /tmp/system.cfg and hit enter.
5. Hit the i key so you will be able to edit the file.
6. Edit the following XXX using the Country Code from the provided link below.
7. Hit the following ESC key, : key, wq keys, then enter
7a. This saves the file.
8. Go back to your web gui, and hit the wireless tab or refresh the page.
9. You can now change it to whatever country you like.
Note: If it is a US model, then you will still only get the US/Canada/Puerto Rico options.
Country Code List: https://wikiinfotechno.wordpress.com/2015/08/06/list-of-country-code-ubiquiti/