I can only speak for someone applying out of the northeast. Having done both undergrad and med school in the northeast I had zero ties to other regions. I applied very broadly (including the south, midwest, and west coast) and still got interviews almost exclusively in the northeast. Out of 21 interview invites, I had only one from the midwest and one from the south. Overall, I got the sense that more academic "prestigious" programs were more willing to interview from all over the country. You can always look up the current resident lists on a program's website and see where most of their residents went to med school.This one goes for all the matched ortho brahs, what did your interview trail look like? In terms of location. I'm interested in going to a region I'm not originally from. I'm always heard there's a bias but is this true or just overblown
Also, don't do an away rotation strictly to "open up a region." The sense that I got was that you really are only helping yourself get an interview at that one program, so make sure you really are interested in that program. Unless you get a good letter from a well known surgeon in that city/region, just having done an away in say, california, won't help you get other interviews there.
Finally, this is only coming from my experience. There's so many applicants from the northeast that I'm sure a large regional bias comes into play, and that may not be the case with other regions. Also, my advice would be to just apply to anywhere and everywhere you might be interested. You never know where you will get invites and now's not the time for skimping on a few hundred bucks. Good luck!!