I have a question, if I buy google stadia in USA, can I choose Italian language, and use it in Italian? And if I buy a game in stadia, can my game work in Italian language? Thanks .
yes that is possible. I bought Stadia for example in UK and I can play the games in German. But it depends on the game, not all games offer the language you want, so before buying a game, I would recommend to check the available languages in the details (when you open the game) in the Stadia Store.
Here is how to change the language of your chromecast in the Google Home App:
Hope this helps!