No. US import laws don't allow for the registration/importation of non-US market designed cars - they've gotta meet DOT crash standards and emission regs.
The only exception would be if the car belonged to a consular official, or someone temporarily on the US; a tourist or military official, for example. But that would be extremely rare, due to the costs involved (especially for something like a Seat). Here in Canada, specifically Vancouver, we let in any car over 15 years old, no matter where it was produced, or what regs it meets. That's why we're seeing some pretty sweet cars from Japan/Europe; lots of Skylines/RX7's/300zx's/Silvia's that North America was deprived of, as well as some nice rides from Europe, like Lancia, Alfa, euro Ford's and the like. Vancouver is also host to a ton of embassies and consulates, so its not rare to see new European cars around (they've got unmistakeable red license plates). I even saw a TVR Sagars a few weeks ago...that's a once in a lifetime sighting for anyone in N.A.! And I have seen some of said cars on my frequent trips to Washington, all of which had B.C. plates.