Wisconsin is ahead of Iowa when it comes to non-conference schedules. I'm not sure that Nebraska's non-conference schedule has been (or will be) that much more difficult. We do occasionally have a quality OOC opponent, but not always. 2023 and 2024, our only P5 opponent is Colorado (a dreadful program with one winning season over the past 16 years). Yes, we get teams like Tennessee further down the road. But that's not any better than Wisconsin.
Wisconsin schedules...
2021: Notre Dame, (Army, 9 wins)
2020: Notre Dame (cancelled, Covid)
(2016: LSU)
(2015: Alabama)
2024-2025: Alabama
2026: Notre Dame, (Pitt)
2028: Utah
2029: UCLA
Iowa doesn't have any non-conference opponents near what Wisconsin does -- even looking forward the next several years. Iowa literally does not have a P5 team scheduled other than their rival, Iowa State. Wisconsin has a legitimate P5 opponent (or greater) on their schedule more years than not.
Iowa's future schedules...
2022: Iowa State, Nevada, South Dakota State
2023: Iowa State, Utah State, Western Michigan
2024: Iowa State, Illinois State, Troy
2025: Iowa State, Florida Atlantic, UMass
2026: Northern Illinois
2027: Ball State