Congratulations @Aurél!
I want to say a couple of things in response to your question. First, if you are admitted, that doesn't mean you are obligated to accept the offer. How many programs did you apply to? It might be wise to wait and see if you receive other offers, and then begin to weigh which ones you are most interested in. I think it's generally good advice to visit the campus before committing to a program, to see if you like the vibe of the department, if you get on well with your advisor, etc.
I don't know much about USC's AMST program, but the university itself is a great school. Perhaps others in this thread can speak to the specifics of the program.