Hey! Congratulations on the acceptance!
I did my masters at USC, and while I can't speak to the American Studies department there, I can confirm that it's a good school, with some great work happening there! It's a good place to be if you're interested in social justice, as it's a place where a lot of conversations are happening about that, especially in the graduate community. Activism at USC is definitely alive and well, even when it comes to students looking critically at the institution itself (there's an interesting ongoing debate about the building of walls around USC, and its physical and symbolic isolation from the community surrounding it.) LA is also a good city to go to if you want a holistic learning experience--I personally learned a lot about race, gender, and sexuality outside of the classroom on the streets of LA.
I was also there as an international student (from the UK) and they put a lot of effort into making you feel at home there, if you sign up to attend international student events. If you have any questions about the campus or area, feel free to send me a message! For example, USC has an awesome campus, but isn't in the safest part of LA--do you know anyone in the city? Have you thought about housing at all? Have you had a chance to visit?
From what you've said about the program and your interests, I'd say go for it! But if you want to know more before making the decision that's smart too
A x