Autonomous vehicles can't rely upon V2V comms. There are far too many ways for such comms to degrade.
And if you expect you can force non-connected cars to not exist on rural roads sometime this century, you are delusional.
Exactly 100 years ago they outlawed horse-drawn carriages from the streets of New York City (https://www.nytimes.com/store/horse-cars-last-days-1917-nson...). Based on that, I cannot imagine what the roads will look like at the end of this century, but is it inconceivable that manually-operated cars will look as outdated as horses?
Could an anti-social person cause a bunch of cars to crash for kicks? Could someone with an axe to grind cause a bunch of cars to crash in order to further his goals?