>>If the EU is politically forced into accepting the US standards: The slack will need to be picked up by European insurance companies, who should charge extreme premiums for unsafe designs, effectively blocking the sale of the vehicles from dangerous, young, or casual drivers and limiting those designs to those who truly need them (which I suspect is very few.)

That only works if there are big penalties for killing people with your car. As it is as long as you are not drunk and have your license you get away with a minor slap on the wrist. You pay if you damage someone's else car but if you kill them then there is usually no financial responsibility and thus no reason to rise insurance premiums.