The collision tests are normally based on the collision with a static object when the tested car runs at a speed of 60km/h. Normally, the impact force is smaller for cars with smaller mass. So, most of japanese car can easily win the score. If you drive a Camry and collide with a similar American car like Ford Taurus head-to-head, most likely, the driver in the camry will die but the drive in Ford Taurus will survive. I saw too many examples. Of course, Japanese car is more reliable and gas-saving but with a cost.