2 wheel transit requires actual expertise unless limited to mediterranean climates. you also have no way to deal with practical concerns like injuries, spare tires, designated drivers, and transit of things like gear for sports. that is all stuff that is the bread and butter of yound people needing cars/transit and why the parents delegate it out.
on the flipside, smaller cars & motorsycles are more dangerous. EG, when hit by all the massive SUVs and crazy f150 class vehicles favored by commercial drivers.
their is a logic to why americans drive the cars they do. in part that's why the story is more akin to a tradgedy than a farce. the issues don't solve themselves with trivial remedies.
Untill their is public transit that is safe, all-weather, and comprehensive, the public will need de-centralized and private transit solutions.
unfortunately, the geographic and population topography of the country does not suit the european model of public transporation. there are also many issues now that it is "too late" to save places like california, who now have such massice entrnched residential real estate that new transit corridors cannot be built by the state without paying in essence ransom to current deed holders.
...etc.