Artists on Spotify are not publicly tied to a specific country, and are simply "on the platform", therefore you can't get all the artists from a country. Spotify may collect details about their country based on publicly known information (such as their Artist bio), Spotify Premium subscription, Spotify for Artists account, or tax details, but none of this data is public (for obvious privacy concerns, primarily for smaller artists).
As mentioned by oda, you may be able to determine what (artist's) songs are available in a market, however this only tells you if you are able to listen to the song in your region. You can achieve this either by using the available_markets response on the Get Track endpoint, or searching by market as oda mentioned.
how can I get every artist name from specific country? Is this even possible? I tried and I didn't find it
Spotify API (spotipy) - get artist names from specific country