This issue comes up every year and I am equally enthusiastic and frustrated by it. The fact is that Carrie is specifically creating and designing a career that is "specifically" intended to exist within the country sphere.
So she really does not have a set list that is going to get 100.000 football fans, and millions of viewers, on their feet for 15 minutes.
I am kind of on Team-Adele. Know your audience and do amazing things there! There is NO shame in not doing something like the Super Bowl. For someone like Adele, its garish and pompus and over-the-top exploitation. And she is kind of right. That is not a wrong thing. IT just is what it is.
When Carrie did the National Anthem, I appreciated the opportunity and the specifics of her participation. (I did not like the performance, but that is another post). But headlining, it suggests that the artist has a universal appeal that has been sought and won. And this is the prize. Sadly, Carrie has avoided the "big stage". She likes where she is and doing what she is doing. And she seems more commited then ever to staying right there. So, that is a sacrifice for someone who has the wide appeal she has. But it is hers to make.
I believe she could, and could have been one of the biggest names within music today, and could have a catalog of music that could easily fill 15 measly minutes. But that does not seem to be what she is focused on. So there for, but the status that she has chosen for herself, I can't really see her doing a full halftime show at the Super Bowl without pulling in other artists.