Just thought of something here.
Canada has a national health care system, the USA does not.
Canada has mandatory helmet laws, USA does not.
Think about that one for a moment....
Part of the issue with 'free healthcare' that people have is it comes out of their taxes. That means either taxes go up, or some other service gets degraded. However this also means that your tax dollars are paying to fix other peoples stupidity, including Smoking, excessive McDonalds, and yes, even not wearing a helmet. So it makes sense to demand safety first by law.
However here in Saskatchewan, Canada, there is no law for a helmet. Manitoba if I remember correctly it's optional as well. Saskatchewan is the only place I cant find even a hint in the lawbooks about gas powered bicycles, so the police treat me (and I imagine any others) as an E-bike: that is bicycle laws, with an undefined "reasonable" speed cap (basically the speed limits posted for cars).
And a side note: No, I don't wear a helmet. As another said, not by choice. I, however, have to special order one, which is quite costly, because of my XXXL head -_-