"Die" is a bad target. I don't want to be a quadriplegic if I don't have to be, and a car going 30 MPH (realistically 40, if the limit is 30) on a residential street is more than capable of doing that to me.
They absolutely can. People can and do die from falling over and hitting their head. A 30km/h impact is not trivial, it can be expected to break bones and cause internal bleeding that can be deadly. An impact to the spine or head can be very easily be life changing.
Also, residential roads in the US are usually 40km/h
I personally know someone who was hit at about 10-15hm/h and they were hospitalized and broke their spine.
My college girlfriend was hit by a car right next to me going those speeds during a turn. It seems slow, but meat on steel is pretty brutal at any travel speed. It was a four or five month recovery. Remember that the velocity of the vehicle is only a part of the picture — mass is the damage dealer here.
Mass is what contributes to inertia which allows the speed to be carried for longer... The acceleration, which is the difference in speeds, is the real damage dealer.