Those countries also have a higher number of brain injury cases vs countries where people wear helmets.
If you are hit by a car a helmet will do approximately nothing. However there are a lot of accidents that happen where you are not hit by a car where a helmet will help. (and even more when knee and elbow pads are what you need)
A helmet can make a big difference in saving your brain if you are hit by a bike. Or if you hit a slippery spot and fall off your bike. Or - hundreds of other things that happen.
cars are too big and heavy for a helmet to make a difference - but they are not all that can go wrong. Even in car heavy US there is more than a car that can harm you.
Well unironically you would be safer if you did that! Although it's a trade off between looking ridiculous and being safe. I personally don't think bike helmets should be mandatory because it puts people off riding a bike (including me), but do acknowledge that they do make an individual safer.
If you are hit by a car a helmet will do approximately nothing. However there are a lot of accidents that happen where you are not hit by a car where a helmet will help. (and even more when knee and elbow pads are what you need)