Hey @Tyrone2020,
you can keep an eye on the social media channels (Twitter, Facebook, Reddit, etc.) or on the Google blog (blog.google.com) for Stadia news.
Recently some more countries have been added for Stadia, but if the team adds more, you would hear/read this as well on the above mentioned channels.
All you can do until then is to leave feedback for the Stadia developers in which country you would love to see Stadia (simply tap your profile picture in the top right corner on stadia.google.com or in the Stadia app and select "feedback").
