The breads that are cheaply available in grocery stores are not very good. Kind of like unflavored and unsweetened cake, to be honest. Of course, if you take the time to go to actual bakeries, you can get some nice breads. But given that convenience is king here, finding good food can become a bit of a niche hobby rather than a regular practice. Some towns, decent eats can be nearly impossible to find and if you want what's best for you (and best tasting), you are better off growing it yourself.
The corn thing is pretty absurd. Mostly, it's due to gov't policies from the 1970's (maybe earlier). So much corn is grown now that most of it will rot before it can be used, so industries have been built solely to process subsidized corn into whatever it can be made in to before it goes to waste.