There is one possible loophole but never tried it. Europeans can bring cars into the USA for temporary personal use but must agree to export the vehicles. However I have heard of German & other European military coming to the USA & bringing their cars with them. In some areas they have to register them locally. Once registered in a state I have heard you are "home free" & if sold, apparently is treated like a legal American spec car. I have heard the feds don't follow up to see that cars brought in legally for temporary use but they might if someone makes a complaint to the proper authorities. You might also have problems getting insurance on the car. I wouldn't recommend doing this since you might possibly lose your car. My favorite cars are Citroens but Citroen has been out of the U.S. market since 1973. I do have a 1979 Citroen CX diesel "gray market" car which someone else brought into the USA & had it legally converted to USA specs. Its a nightmare I wouldn't want to go thru & understand after the early '80s it became much more difficult because individuals were bringing in M Benz Euro spec cars they could then buy new in Europe for around $13,000, pay $1,000 for shipping, $3,000 for conversion to U.S. EPA-DOT specs & sell them at a nice profit for less than the M. Benz wholesale USA cost for similar models then carrying a MSRP of $30,000. I heard that M. Benz, BMW, & Porsche then lobbyed congress to get the law changed so that the manufacturer could state a vehicle of theirs DID NOT meet USA DOT-EPA specs even though it actually did since some country's specs (Sweden & Japan) for example, exceeded USA DOT-EPA specs except for some minor issue like installing a serial number in the left bottom windshield area visable from the outside.
I resent such laws & I presume most of you do too.
I think it would be far more inexpensive to import diesel engines & related accessories & convert gas engined VWs & other cars to diesel but you would have to know these cars inside & out, what differences exist between similar gas & diesel models, etc. Does anyone know anyone making these conversions? I think someone could make some money here if they lined up a reliable source in Europe for wrecked TDIs with good engines, imported them & installed them in gas VW Jettas, Golfs, etc.
It is my understanding that if a car is 25 years or older, you can now import any such vehicle legally & not have to modify it to DOT-EPA specs. Before doing so, I would carefully research U.S. customs regulations to make sure this is legal & don't rely on my info here.