Please see "Availability by Country/Region" at the bottom of the official website for a list of the countries in which Mario Kart Tour is available.
Notes:
As of May 31, 2023, you can no longer choose Russia as your country when you create a new Nintendo Account or change your Country/Region in the account settings.
However, please note that players whose Country/Region is currently set to Russia will still be able to play Mario Kart Tour.
We appreciate your understanding and cooperation on this matter.