Hi, this information is obtained from your public IP, something that others on the network can also obtain, and web server you visit have access to. The database that Avast uses is a pretty good one, but apparently, it contains errors such as in your case.
If you are OK with the level of details that is exposed, you can ignore this. Such as if you are actually located in a different state or city, then you are probably safe and can ignore this warning -- for other users, even a rough location is too much and they use VPN to change their appearance on the network, such as to present themselves as being connected from a different country.
