Paramount+ connects you to a local station based on “location services” of the streaming device. There is no location setting to change or ‘fix’ this. It is not an account property or app property, but a device property. “Location services” can be very precise through cellular connected devices. For devices on your home network, your local IP address (as leased from your ISP) would likely be used to map that to a location (by best guess approximation through one of many third party lookup services), as I’m not sure what other data could be available to base a location on. Maybe detected Wi-Fi hotspots can also be used to help determine a location. A VPN service on your network might confuse location services, so disable that if present.
Verify that you have activated Location Services in Privacy Settings.
Verify that you allowed the Paramount+ app to use Location Services on Apple TV.
Else try contacting your ISP to get a new IP address that better reflects your actual location for IP-to-geolocation lookup.