Munchkin,
You are correct. The university does not count U.S. citizens as international students. I was calling these students international as many of them never lived in the U.S. They may have a very different point of view about Greek life than someone who was raised in the U.S., particularly in a southern state.
USC states on their profile international students do not qualify for need based financial aid. Alumni have donated funds for a small number of highly competitive merit scholarships for international students.