I prefer "I Know You Won't".
For my taste, "All American Girl" has too much of a Mainstream sound - and that isn't really my scene. However I think it's an important song for Carrie.
Co-writer Kelley Lovelace was one of the first to praise Carrie's attitude as a songwriter. I expect a lot of you have seen the article, but here it is again:
http://www.theboot.com/2008/04/30/story-behind-the-song-all-american-girl-carrie-underwood/
The same writers, by the way, have worked with Carrie more recently, either together or singly, e.g on "Good Girl" and "Eighteen Inches"
As Carrie's from Oklahoma, I wondered if her choice of the title and chorus might have been influenced by the film "Jim Thorpe - All American"
Jim Thorpe was an Oklahoman athlete, who won medals at the 1912 Olympics. Giving him his medal, the King of Sweden said "You, Sir, are the greatest athlete in the world."
Later, though, the US authorities stripped him of his medals, on the grounds that he had accepted a small payment for playing sport on another occasion, making him a professional. This was done even though the time limit for objections had expired, and many richer US college athletes in Eastern states had also accepted payments without action being taken. Some Oklahomans resented the action, and saw it as snobbish discrimination by the establishment.
I've no idea whether Carrie has ever seen that film (in which Burt Lancaster played the athlete) - it just struck me as possible, as she seems to dislike injustice.
The only thing Carrie has actually referred to though is that one verse (the baby girl) reminded her of her relationship with her father.