Type approval for the US market in many industries, and 'mandatory' features 'required' by consumers (actually pushed by domestic corps) have always been a huge barrier to entry for potential foreign competitors. Indeed, in the face of a chronic lack of innovation and efficiency in many industries, it's been the only way they have been able to compete. There's no better example than the car industry.

I think it comes down to the political system in the US more than anything ... it's all about money, patronage and pork barreling ... if there's a gravy train, the lobbyists make damn sure the politicians know their electoral future depends on maintaining and protecting it, and together they conspire to ensure that it isn't derailed, even if it erodes competitiveness and scares off inward investment.