I’m still not sure your car thing would match here - unless they refuse to sell you a car that you only use in the USA. I’m guessing these stores are brand owned? Why else would you refuse a sale - even if it’s useless to the buyer

I could see rights come into play - but they usually regulate within the nation.

I would think this is connected to name/address/payment not matching the country you claim to live in. If it’s VPN detection then a WiFi router doing the VPN would work fine.