Mr. Orci told me that any changes to canon will have an explanation based in canon. I hope there is a good reason that the Enterprise is conveniently being constructed in Iowa where Kirk grows up. However, I am holding out hope that people around here are taking the scenes in the trailer out of context and that scene does in fact take place closer to San Francisco.
Here's the rub. The movie is supposed to open with heresy! In other words, something right off the bat is going to either be a blantant breach of canon, or something is going to happen to change time.
My guess is Kirk was born on the Kelvin on during Nero's attack on it. He, his brother, mother, and many others escape while his father takes command of the doomed Kelvin and fights for time. This wasn't supposed to happen.
Kirk's mom remarried and moved to Iowa. Either they are from there, or perhaps Kirk's stepfather is somehow involved in starship construction there. Or, since his father was in Starfleet, that could also explain why his father and mother called it their Earth home. Like military folks today who have homes in or around bases.
In other words, there's nothing convenient about the Enterprise being built where Kirk grows up. Either his family simply moved to where his stepfather's job was, or they lived there because Starfleet has a presence there.
At least that's my explanation.