I want to change the Region via Terminal. How can I do this ?
Ideally it would use a command (/usr/bin or sbin) or modify a plist (plistbuddy).
I'd love to avoid using osascript (AppleScript)
The region is stored in
~/Library/Preferences/.GlobalPreferences, as the second part of the AppleLocale variable. Some examples of the AppleLocale variable:
You can get more info from Apple's Developer Library, which also has links to the ISO 639-2 codes that can be used.