I understand that certain American vehicles can't be sold in Europe due to their length being too long (hence the shorter length of a particular late-model Chrysler hot rod sedan so it could be sold internationally, aka the "Five Meter Car"). Over there, I believe it's done by taxes, just as it is on engine sizing and similar. I also suspect that's a reason the more recent USA vehicles are getting narrower too, becoming basically 4 place automobiles.