The CC issue as other ADCOMs have said in the past really is overblown here on SDN IF you do well after you leave your CC. That's the big if and something alot of CC transfers struggle with. If you have a 4.0 at your CC then come to USC and get a 3.25 your next two years, that'll definitely be a problem. But if you can continue to be a good student at USC(think 3.7+) your academic record alone is sufficient for a ton of medical schools, even some of those bigger names you cite.
Bottom line just keep doing well. Manage your schedule appropriately. If it means going light your first semester to adjust, that's a smart decision. Might be a good idea to just take Ochem II without Calc II next semester to adjust. No one will care if your first semester from a CC if you just take Ochem II and non science requirements if you do well; the alternative of taking more tough courses and having a greater risk of doing poorly might not be the best option.
When talking about medium/high tier schools the MCAT really is king there. Schools like USC and Stanford have 35+ MCAT medians; far far easier said than done to achieve. But keep doing well and you'll put yourself in a solid position. EC's for these bigger name school are major factors as well; if you need to take a gap year or two to boost your EC's while focusing on academics while at USC that's a very solid plan as well.
Keep doing well, and keep rocking your ECs too. Take advantages of all the opportunities at USC to further strengthen your application. I was a transfer from a California CC to a 4-year in NY, and I chose to take a gap year so adcoms will see two full years of my grades at my 4-year, plus all the long-term activities I did there. I took all the pre-reqs except for physics at my CC, and I think I'm doing pretty well this cycle. PM me if you have more questions - I'd be happy to help and give advice.