Even US drivers are not quite heavy enough to make a significant difference here. This has to do with car battery weights.

Fat car can hit an innocent skinny car on the other side of the road, in case of an accident.

The problem is if they crash through the guard rail and kill or Injure others.

Yeah you say that now but when that article comes out about all those kids in a SUV dying you will be upset that the government cheapened out.