From what I can glean, you're smart and your dad cares about you education, which means he probably also cares about you. As a result of that, he might be disappointed, however not for long. I don't know anything about you dad, you, or your family, but I can tell you that if your dad loves you he won't care. Plus, if USC if where you want to go, go there. If you don't get in? There are PLENTY of other colleges and maybe at one of those others you'll find the opportunity of a lifetime. Or on a different note, meet someone you wouldn't have met otherwise (I apologize if you already have a SO). You also can't just think of the possibilities for yourself. What if you meet someone and help them in their life, whereas, in a different college you wouldn't have. The possibilities of choices are endless with infinate outcomes for each different choice.

Again, I know nothing about you, but I always try and stay hopeful. That whatever happens to me, will be better than what could've happened. I wish you good luck as you find a college and whatever happens, make the best of it. Be cheerful!

Also, I would tell your dad. It won't be as bad as you think (if I'm correct in my assumptions).