Comparing US statistics to Dutch ones makes no sense. Their roads are several times more deadly than European ones regardless of vehicle.
Furthermore not all of their states have mandatory helmets (!) whereas over here it's rare to see someone missing something other than pants. Except scooters, scooter riders are under the impression that they don't ride a motorcycle and that flip-flops are appropriate apparel.
Then there's a lot you can do as a motorcyclist to mitigate risk. Riding safely is one (not everyone seems capable of that, there's quite a spread in riding behaviors, but also an obvious bias in which ones you'll remember seeing on your commute). A strict no-alcohol policy is another, and not riding at night on weekends. You can also wear extra safety gear such as a high-vis airbag.
Also licensing requirements. Oh and American motorcycles don't have to be equipped with ABS. They be crazy over there.
So... Cotton/Linen/Wool? The technology is fine, its only downside in most applications is simply cost. Cotton clothes are more comfortable, less stinky, less polluting, and won't fuse with your skin and disfigure you for life if they accidentally catch on fire. On top of not making microplastics soup every wash cycle.
If we cared to actually solve the problem of plastics in fast fashion we could ban them, with some exceptions for sportswear and shoes where synthetics have some actually useful uses. Hell, we could even make it an easy transition by gradually pulling back the allowable synthetic content for x years.
But it would directly kneecap Shein and H&M's business model so we have to weigh all the pros against that.