Also, I think your idea that cars themselves are the problem is probably incorrect. Decarbonization isn’t primarily about reducing overall energy use per person, although you can possibly deflect with the argument that it requires both that and also clean energy.
In any case, American culture and cities are car culture and cities, and even if you could do the impossible and magically deploy tons of HSR between every metro in the US it wouldn’t make people stop driving. Any solution that requires first rebuilding the whole country and replacing its whole population with people who don’t want to drive a large vehicle to the grocery store is obviously a nonstarter.
Tesla accelerated the electric car market several years, that's for sure. But nothing more than that.
The most important development for the feasibility of electric cars has not been automotive innovation (not the powertrain, the motor, the wheels, the interior or whatever), but battery innovation.
And battery innovation (i.e. cheaper, lighter, more capacity, better heat management, better durability) has been ongoing regardless of automotive even existing as an industry.
This has been the driving factor for the electrification of cars, not any one car company but the battery industry. Tesla simply was the best first mover.
https://ourworldindata.org/images/published/Battery-cost-dec...
