The USC in your example stands for United States Code. So in the example of 15 USC 1681 it would refer to Title 15 of the United States Code Section 1681.
18 USC § 922(d)(6)
USC defeated Michigan 32-18
The USC Trojans beat The Michigan Wolverines 32-18
USC Title 36 (United States Code, Title 36)
Title 18 USC
No. In the majority of US states an 18-year-old is no longer under the custody of their parents. In the few states where the age of majority is higher than 18, there are federal laws (18 USC 2243 and 18 USC 2423) that forbid a minor living in one of those states from crossing state lines without parental permission.
USC
Copyright law is US Code Title 17, and fair use is section 107 of it.
No, but they can serve time in jail, pursuant to USC 18, Sections 702 and 704.
Define "USC", there are several companies and a university using USC
USC trojans