I’ve been looking around a lot for an answer to my question, but can’t seem to find it on any website, USC’s or otherwise. My question is if a merit-based scholarships are given in addition to the need-based grants offered by USC. I am a National Hispanic Scholar, and I believe that qualifies me for the National Merit Finalist scholarships. With all this being said, would USC offer me the $26,000 for that scholarship, along to however much they may give me in need-based grant money, for example ~$30,000 ($56,000)?
National Hispanic Scholar does not qualify you for the National Merit Finalist scholarships. Those are two different things. Also, the merit aid would just substitute for the need-based aid. So, if they offered you a $26,000 merit scholarship and you had $30,000 of need, they would give you the $26k in merit and $4k in need. The theory is that if you needed $30K and then receive some merit money, you now have less need.
National merit finalist awards are based on your PSAT score. If you are a National Merit winner, they will offer you the ½ tuition scholarship, however, it is only ½ tuition. You still need to fund the other half of the tuition AND, you also have to fund your Room and Board on your own. Can you afford that? The fees for USC are expensive ~$72K per year.
The National Hispanic Scholar is a label. It doesn’t bring anything financial with it.
The National Hispanic Recognition Program is also an honor. You receive that title if you score very well on the PSAT. No money tied to it.
Yup, just as had been said above, the merit aid would likely chip away from any need based aid. For instance, I was applying for the Topping Scholarship and the award is typically 5K, but could cover up to full tuition (at least according to the Topping Scholar I spoke with). She made it very clear that even if we were awarded the minimum of 5K, it would reduce any need based aid such as the university grant (which USC is quite generous with). It basically came off as her saying that USC doesn’t like to leave you with a surplus of money 
they want to make sure you get just what you need. In my case, USC covered my tuition with need based aid. I just had to figure out room/board and insurance costs (I was uninsured during my time at USC).