huge. Nobody could tell you who won the BYU-Utah game for any of the last 6 years, but ask them who won the last two BYU-Texas game. They know and they will tell you all about it.
I live in Cincinnati now and I have a Y helmet in my office. People stop by to talk about BYU-Texas, Toledo, Cinci, and West Virginia. Nobody EVER brings up BYU-Utah.
My BIL is a Husker and lives in Lincoln. He painted his house red and lives and dies by Husker football. He said the same thing about his area, people knew about BYU but had little respect for the program compared to their own. He didn't grow up LDS and knew nothing about BYU but he and his friends gained a lot of respect for the cougars.
Beating Utah on the national scale doesn't move the needle. It doesn't even register.