i don't think so.... if the gov't found out kiss it goodbye...
i've imported my supra fron canada to the US... i used to live there. there is a lot of paperwork to do... and you need a letter from toyota canada saying that it meets or exceeds all US codes.... since mine was a canadian one, it was no problem, however RHD cars are not permitted.... basically wherever your car came from, that's where you need to get the letter from. So a JDM car will need a letter from Toyota Japan. Even if you do manage to forge the paperwork and submit it to customs (which is not hard) and get it registered... they do send it to toyota canada or wherever to get verified... so you can kiss your car goodbye if you do that (and perhaps end up in jail)
Only other way would be to import it from japan to canada (which can be done I believe) ... register the car there, even with a temporary permit.... and then drive it to the US (make sure you say you are "JUST VISITING" at the border.... don't say you're bringing in a car).... then you simply take all the VIN #'s off from a donor US market supra and put it on the RHD one... but that is not 100% legal either and I'd still be very careful. I suppose you could always say you bought a supra clip from oversees and converted your supra into RHD. Whether that will fly or not, I'm not sure.
Also, I've seen 2 RHD supras, and a couple dozen skylines for sale at the US government customs auctions for seized vehicles:
http://www.treas.gov/auctions/customs/vehicles.html
There aren't any there for sale right now, but they always say (For export out of the US only) next to it, meaning someone brought it in and had it taken away to be exported back out.
So I'd be careful and do your homework. If you're getting a Japanese market vehicle, Get a VIN# for a car you want, and call up Toyota Japan and ask them to give you the paperwork for that car to be imported to the US. If they say "Sorry no can do" then that's your answer.