By default, the steam country may be set to you first sign up Internet Protocol (IP) Address, or when you first purchased game in Steam.
But you can check according to link, or search youtube:
Furthermore, You can also change it. But this is for you to change it every 1 year or more. No as you like.
If the store country has been changed in the last two weeks or a purchase was made in the previous country within the last 48 hours, you will receive a temporary cooldown on your account. The cooldown will prevent you from changing the store country for a period of time.
Note: Steam Support will be unable to assist you with changing your store region.