I lived in Mississippi for four years and they definitely took offense in the small town I was living in. The size of the community might also be relevant. I’m not an ethnolinguist, so can’t really comment on why it is or isn’t.

Take the map for what its worth, I guess. It doesn’t comment on what people think about the word itself, just how they don’t use it very much.

I'm just wondering if there are areas where "you guys" can't be used to refer to arbitrary-gender-makeup groups (as opposed to areas where it's just less common than other phrases accomplishing the same purpose). I haven't personally encountered such an area, but I accept and acknowledge that you have.

I do think this topic is complicated by the ease of conflating current usage (how is "you guys" used today?) with ideal usage (is this really a phrase whose usage we want to promote and accept in the future?). I personally have no problem making an effort to phase out "you guys." It's not something I feel attached to, and I can see that it carries unnecessary baggage.