The selected country should be the country you currently operate from. This has to do with competition and payment related purposes.
You can still participate in tournaments in other regions than your own, if at least 50% of the team (for duos and squads) belongs to the region a specific tournament is held for.
If you would like to change your country please submit a request where you state which country you would like to change from and to which country you would like to change to. Make sure to also explain why you want to change your country in order to have it reviewed accordingly.