As I remember, the US military would ship cars back to the States. I don’t know if they still do that.
My brother who was in the USAF in Germany shipped back a VW van ~ 1977. I don’t know if he paid for the shipment.
They wouldn’t ship them free for us back in the late 60s. Would’ve cost us an arm and a leg. Thus I just handed my keys to a “friend” (he was supposed to send me $50, yeah right!) and walked away when it was time to go home.
I was in the USAF, in Japan, in 1987. DoD would have shipped my car back to the states, if I'd wanted them to. I was offered a Japanese 1971 Datsun 240Z with a racing cam for $500. That might have been worth shipping back.
Only things you have to do to get your car shipped (at least in 1987) is drain the motor oil and coolant, and bring the car to US specs. Usually means replacing the headlights and windshield, nothing else.
I sold mine to another GI before I left and bought a new VW van which the government did ship back to the CONUS. Kept it for another 3-4 years.