TVR was in the US market years ago. They nearly went bankrupt, so scaled back. Now that they're doing well again, rumors have been circulating that they're considering entering the US again. They supposedly even developed a left-hand drive Tuscan for the US. However, those rumors died down late last year, when TVR denied its intentions to go anywhere that would require additional development funding.
I personally love TVR's. Hopefully soon they'll have enough cash to justify the expense of coming here they'll reconsider!
I would think it would be quite difficult for TVR to enter this market because
1) They make their own engines. The cost of meeting US emissions laws would be prohibitive
2) I do not believe any of their cars have airbags.
2) They are not interested in being a component maker. They want to be viewed as a "real" car producer and a kit would be counter to this
3) They are very small and the market here would be very small.
Unfortunately not a good business case. Not too mention how to enter the market and set up dealers. I think there should be exemptions for small manufacturers like this to allow innovative new products into the US. Anyone who would buy a TVR would understand the plusses and minusses of what they are getting.