I have a 3.5 
Weighted or unweighted? USC doesn’t have a strict cutoff - it depends if your GPA is due to straight A’s freshman and sophomore year and 4 D’s junior year, or if it’s something like B’s sprinkled in all your weak subjects.
A low GPA means high test scores and excellent writing and recs become relevant.
I had b’s in all of my weak subjects. My stats are posted if you want to look at them 
3.5 Unweighted?
According to the 2015-2016 common data set, USC had 24.6% of their enrolled Freshman with an UW GPA’s between 3.5-3.74.
http://oir.usc.edu/common-data-set/
What about test scores? LOR’s, EC’s and essays. All will contribute to your chances.