Plan and simple if its not at least 25 yrs old it cant be imported into the US.
On the Skylines, I believe the R32 did get clearance to be imported as it went through US crash testing and did pass. The company who got the certification for the R32 then forged the results for the R33. Some were imported under that forged paper work but they were found out. The US sent out Feds to confiscate R33. One of which was taken from the guy who ran the R33 skyline forum.
Yes there are ways around but nothing is legal and if you get a smart cop, the car is gone.
Im upset my phone has recently crashed. I was going to post pics of the only Nissan Stagea R34 wagon here in the US we currently know of. A friend has owned it for a number of years now. Bought it feom an importer in Flordia. Yes, it was brought in illegally and the plates on it since Ive known him have always been out dated out of state plates. Like 7 states away. The car is actually trailered to shows and currently is just hidden in a garage.
Here is a google link to pics of the car and him.
Now a little about importing a car that isnt 25 yrs old and you want to do it legally. Well, you would need to import 3 actually. 2 of which will be crashed. 1 does a front offset crash, the other a side impact test. If they pass, the 3rd you can keep and drive. If one fails, you can make improvements but they will need to rerun the test on an undamaged car that got the modifications.
Things the US doesnt like, glass headlamps, no true bumper reinforcement, no door beams and thats just to name a few.
Other ways I know people have used to drive say a real RHD Civic or Integra that isnt 25 yrs old yet.
They have the RHD car, say a white 2dr Civic, then get an identical LHD White 2dr Civic car, plate the LHD car and put those plates on the RHD car. That way when the cop runs the plate randomly it come up to a White Honda Civic. Granted, if you do get pulled over for something, again it comes down to how smart is the cop that pulled you over.
I do NOT condone anything I just put out there but was ONLY using it as examples of how people get away with it.
Some things you may want to read over if interested in importing a car.