I beleive that in the US, dealers will not sell RHD cars because they know they will be impported into the UK. This then interfears with the UK importers area, who loose a RHD sale.
Tried it before and never found one who will budge as the MFR just won't supply them the car.
But they have no choice if you want LHD.
If you go stright to export from the dealer I think you avoid state sales tax (6% in florida).
What car are you thinking of?
What makes me angry is fully loaded Range Rovers are cheaper in the US than the UK by 30% and we make them and export them!!