Difficulties in achieving NHTSA compliance and overcoming import/export taxes to achieve a marketable price are the general culprits. The US and Europe have much stricter safety and emissions standards than most other countries, so that plays a role. (For example, the Jeep Liberty CRD diesel model was cancelled because the engine's emissions couldn't meet new NHTSA standards.) And market pricing is a big problem - imagine how hard it would be to sell an Indian SUV in America if they can't get the base price below that of a new Kia or Hyundai.