Why I can't find Serbia when I am signing in to Facetime?

I am trying to set up Facetime on my Macbook Pro M1. When I am trying to find a country, I am not finding Serbia on the list of the countries. Why is that so? I assume for the same reason I am not able to log in to iMessage.

Just please do not tell me to restart my device or something similar because you have similar topics regarding this, and it seems the support is doing nothing on resolving this issue.