You don’t have to worry about that at all. I myself live on the East Coast of the US, and I have never seen any of the states that the majority of the show takes place in. Even the filming for the show is done in Canada. I’ve found google to be a great research tool for when I need help.

Plus, the boys went to Ireland in one episode of the show. Though I’m not sure how they’d smuggle Sam onto an airplane, especially with Dean’s fear of flying and no Sam to strong-arm him onto the plane.