Energy of a car
I conceed to each and every point. I was already coming up with other possibilities regarding the beer can/styrofoam scenario:
There would be a certain speed at which the beer can does not crush, but bounces off the styrofoam (go ahead and use your head if you want, it's still a free country). This would be the maximum speed for the elasticity of the can. At a slightly higher speed, the can would crush, and not bounce. The inelastic collision would cause less damage to the styrofoam than the elastic collision at a slightly slower speed.
Back to the car: Cars are designed to have minimally elastic collisions, so this scenario would not apply. I still am convinced that as the speed of the car increases, the amount of damage to both the car and the tree increases.