Nebraska hasn’t been a contending team since 2001. USC hasn’t been a contending team since 2005.
USC has potential to get back to a perennial contender if a coach can emerge that just locks down California recruiting and can poach nationally. I do not think Nebraska can ever get back to their heyday. They’ve only ever won with one style and that style is gone. No elite recruits actually want to live in Nebraska.
I can see 5 teams from the Big10 ever actually winning a modern title: Ohio State, Michigan, Penn State, Oregon and USC. I’d be willing to bet good money no other team from the Big10 will win a championship in the next 10 years at least.
In the SEC, there’s 8 teams (Bama, UGA, Texas, OU, LSU, Auburn, Florida, Tennessee) that have won since 1998. That’s literally half the conference. I could also see TAMU or Ole Miss contending for national titles in the next 10 years.