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A state school likely has a variety of majors, including liberal arts degrees; not just STEM. You should be bumping into those students in your general education requirements (philosophy, writing/speech, arts, etc). You might find more diversity in those classes, that the entire student body has to take, although maybe not. When you have to take a non-program elective, make sure you pick interesting classes.

If you're looking for people from other countries, your state school probably has an international program (international students generally pay the school's sticker price, which helps balance the books), see if there's some way to get involved with that. There likely won't be as much diversity as at a school with a world renowned program, especially since obtaining visas and crossing borders have been challenging recently, but there should be some.