I'm not sure the type of person who imports such a vehicle would have the appropriate amount of foresight to let such a law affect their behaviour.

What amount of foresight allows one to endanger their own children more for some completely hypothetical 3rd party?

Driving around a big SUV/truck is usually safer for your own children travelling inside. Since the public has basically gifted me a gigantic subsidy, society invited me to play prisoner's dillema and protect my own kids at the cost of everyone else. Until I had kids I rode a motorcycle full-time as I had no one under me and I could take additional risks for environmental concerns. After I had a children I bought a McTank because basically my kid will be protected and the loss is socialized to everyone else.

However, if public stops subsidizing me I would go back to a small efficient car. Because then I would save so much money it would go back to my kids being better off as it would be enough difference to be made up for in better education, healthcare, etc.