I would first suggest looking through this excellent thread…
I also concur with the sentiment offered by @jmek15
USC is not really interested in a laundry list of clubs, honor societies or activities. USC also turned away 1000s of kids this year with near perfect stats. They want to see how you can differentiate yourself somehow in an applicant pool of 55K+. USC would prefer to see how you dedicated yourself to one true passion, possibly exhibiting leadership or responsibility roles in that one key area. Admissions will expect you to have a solid, well-thought answer to “Why USC?” And they will want to be able to picture you there at USC in the future, helping the greater USC community by your involvement and interactions in some manner. So… to balance “Why USC?” from your perspective, maybe also think a little in terms of what USC can expect to be getting from you and your involvement there. If what you may be able to offer is something unique or unexpected, even better.
Good Luck