Nation

From the start your nation was detected based on your IP adress. That system can sometimes make mistakes, or you can simply live in another country.

That is why you can change your nation to another (not only to real life nations, you can change your nation to Red Cross, UN, etc.). But your original nation will still be shown in your profile (hover mouse over nation flag).

You can change your original nation too, but you can do it only once.

Navigate to nation change in your profile

Navigate to original nation change

Select any nation you want, list of regions shows you where you will have a damage bonus

Damage bonus

Your original nation (not your current nation!) will determine the list of regions where you will have a damage bonus while fighting in wars for them. See damage formula for more information.