I have been asked about Utah games many times assuming I am a Utah fan because I am a member. The perception is Utah equals mormon.  Both BYU and Utah fans dislike this, but it is what it is.

Many here believe the myth that BYU is some national brand that all know and follow.  People do know BYU, without a doubt, but it is not at the mythical level above Utah.  People tend to know BYU is a mormon school, but also assume Utah is heavily mormon as well (which is not too far off) without assuming the few bad apples that ruin it.

All can say what they want, but in my experience the above is the case.  I have mainly lived in the northeast, but have lived in the midwest, TX, west coast and grad school northeast.  It has been pretty consistent across the board, the exception is the west coast where people tend to know BYU and Utah in more detail