I do not think one can say with any amount of authority that their lives could have been saved had they worn helmets; GOK if any kind of assertion on these lines can be proved or true; at best this could be only in the realm of conjecture. The accident sequence is so sudden and complicated that it is hardly possible to say if the helmet would have helped or on the contrary resulted in breaking the neck and caused instant death, which is also a distinct possibility, as per some people.
The US is a different question where the ground realities, thinking of Government and the public’s behavior/response are entirely incomparable. My only concern is about some people exerting and influencing how the rest should conduct themselves even when their conduct does not harm the public in general and them in particular. It will be ideal if the so called Samaritans campaign and create awareness among the public about all evils, including the advisability of helmet use, stopping short of bringing in any kind of force.