There are 7 million LDS members in the US. At 40% activity rate, that's 2.8M active LDS in the US, with approximately 1M of those in Utah.
The Houston area has 7M people. So it's not that we have so much more upside and potential than Houston, it's that we do a better job turning active LDS into engaged BYU fans than they do of turning Houstonians into engaged Houston fans. But if Houston can get buy in from that area, they actually have more upside than we do.
(There's another 9 million outside the US but never in large enough concentrations to justify a BYU telecast on CBS or the equivalent in the Philippines. Streaming means that those international members can have some effect, but activity rates are low