Good luck across the pond but if I were in your shoes there is noooooo wayyyy in hell i would bring a US car to Japan. I would deff find myself a Skyline or Silvia, or a RHD Supra as soon as my plane landed haha. No matter how common they are over there, they are NOT common over here and you would be able to come home saying you personally owned one, where as a Japanese guy may come here and buy a Mustang because its not something he would easily be able to attain back home.
And although you may not be able to get on the gas 95% of the time, when that 5% does come around and your still in a 300hp car you're gonna wish you had that extra 300hp to take full advantage of that small 5% . I would anyways
(please dont take anything I said as disrespect as I mean nothing bad or negative in anyway)