If you are a social person who likes to be around people, you can find self-organised groups of people interested in whatever you're interested in on meetup.com, at least in many cities.
https://www.meetup.com/cities/
If you are not a social person and you like having time to yourself, you can still allow yourself to enjoy time alone even after you move to another country. Books, movies, music, art, exercise, meditation and other solitary activities can keep you occupied and content even when there's no one else around.
I think most people need some of both kinds of activity!