Mee, too. But this is one question, you wont get an answer in North Korea. Original US-cars, mainly Vans and SUVs are no rare sights there, also US-spec import-cars appear sometimes.

I tried to ask this two, three times, but this was obviously an inconvienient question. The guide hum and hawed and said "They came from Thailand, via the Chinese port Dalian. In Dalian are sitting ... *cough* distributors"
Of course with "distributors" he meant "smugglers". I kept quiet and haven't replied, that Thailand is implausible, because at first they have RHD cars there and twice, the cars I was mentioning, were real US-versions.

But he denied categorically, that these US-cars came from Okinawa, in times, when the ferry between Wonsan and Yokohama was still in operation.