As described, the cause of the accident is driving too fast for the conditions, inattentive driving and possibly following too close. Every US jurisdiction I have driven in requires a driver to maintain speed and spacing that allows them to stop safely if the vehicle in front of them comes to a sudden stop. If a driver needs to take evasive action to avoid a vehicle that is not stopped, but just slowing, that is one shitty driver. We are all better off if individuals like that are ticketed and get points on their license.