I did have a BMW X5 I purchased in Korea as a SOFA status Gov Employee. It was US spec and the Warranty was 2 years (standard Korea BMW warranty), but once returned to the US, the remainder of the 5 year USA BMW warranty would be honored. I think the only reason it had the Korea BMW warranty was it was purchased threw a BMW dealer there, as a US model. At purchase it was made clear to me that the US warranty would not be available to me while in Korea.
Tesla may be different but you may be fighting an uphill battle. I would say the route you need to take is to contact Tesla to see if they can honer the USA warranty with work performed by a Korean Tesla Dealer. If not possible to make the arrangement, I would then see if they would reimburse me the cost to have the work done if you paid out of pocket and sent them the receipts.
Another situation was a co worker that brought his VW CC from Seattle and it had an important airbag recall while he was in Korea. VW Korea would not do the recall work and VW USA stated that they could only help him once he returned. They did provide a letter to use to ship the car back to the US since you can not ship a car with open recalls.
Finally, My question. I am planning on going back to Korea sometime in the next 2-3 years. I have a Model Y on order ( just today =P ) here but I am considering canceling it if the Telematics (Over air updates, GPS, remote unlock, autopilot, etc) in a US Spec Tesla will not work in Korea. When I bought my US Spec BMW in Korea, I did not know the GPS and the "My BMW App" would not work and I was majorly bummed. Don't want to pay for premium luxuries I can't use, for the best years of the cars life, again...