Don't mind me. Just chiming in here.
Facebook & Instagrams location targeting technology is quite simple - thanks to it's simplicity you're almost always targeting within the region you desire. However, there are instances you could target outside this area.... allow me to explain why.
When you use location targeting, Facebook finds people whose current city from their Facebook profile is within the location you intend to target. Facebook claims that this is validated by capturing a users IP address (highly doubt it) and verifying that it is in close proximity to profile location. They also use your friends profile locations to validate what city you live in.. so if a majority of your friends list is located in Dallas Texas, and your current city is near Dallas, Texas. It's likely you'll be targeted with advertisements in Dallas, Texas.
I've had instances where ads I manage have been displayed in states other than places I had been targeting, when only targeting people that lived in a specified location.
Why I believe Advertisements are displayed outside of Targeting Locations...
#1: Improper use of targeting configuration.
EX. Targeting everybody within a location instead of people who live in that location.
#2: Facebook Location Targeting is more simple than we assume.
EX. Facebook may use your current/previous profile location and friends profile locations to verify where you live, instead of IP addresses to validate your current proximity to this location data.
#3: Retargeting through Special Ad Audiences/Look-a-likes.
EX. You've landed on their website or landing page previously, and are being targeting through custom ad audiences they've built, in hopes to reengage with customers.
Again, this is just my own speculation.