For long time College Footballs fans USC always meant University of Southern California.
I would submit that when the term "USC" is spoken from the midwest region (Okla, Texas, Kansas, Missouri, Indiana, etc.) and all points west, most folks think "Southern Cal", not South Carolina. Going back to the 1950 & 60's, Southern Cal was much more visible and newsworthy than South Carolina.
Thank the news media for that. They commonly referred to the Trojans as "USC". Go to the Notre Dame campus in South Bend Indiana and say "USC". Which of the two do you think comes to mind for them? Of course in the PAC 12, USC is Southern Cal, an original member of the PAC 8. The PAC 8 began as the Pacific Coast Conference (PCC).
Trivia question:
Who was in the original PAC 8 conference?
Cal-Berkeley, Stanford, Oregon, Oregon State,
USC, UCLA, Washington,Washington State.
1915:
PCC was founded with four original members - the University of California at Berkeley, the University of Washington, the University of Oregon, and Oregon State College (now Oregon State University).
1917: Washington State College (now Washington State University) joined.
1918: Stanford University joined.
1922: University of Southern California (USC)
1922: University of Idaho joined.
1924: University of Montana joined.
1928: UCLA joined.
1950: Montana resigned.
1958: Dissolution of PCC.
1959: Reformed as the Athletic Associates of Western Universities (AAWU).
Original AAWU membership included UC Berkeley, Stanford, USC, UCLA and Washington.
1962: Washington State joined.
1964: Oregon and Oregon State joined.
1968: The name Pacific-8 Conference was adopted.
1978: University of Arizona and Arizona State University joined. Named the Pacific-10 Conference.
2011: Utah and Colorado are invited formally and officially change the Pac-10 into the
Pac-12.