Oh boy, this is a complicated answer. Stay with me, there no TL;DR
First, I think the death part has nothing to do with how transportation is organized outside the US. Nor will it influence transit inside the US.
Transportation has been organized by urban development. I don’t know of any example where cars were banned or taxed or otherwise discouraged due to death rates. In America, regulation was the response to automobile deaths; seat belts, removal of steel dashboards and steering wheels, inclusion of airbags, crumple zones, and as of 2018, backup cameras are mandatory due to too many deaths of children behind cars. If you have an example of other countries organizing transportation based on automobile deaths, I’d be interested to hear that.
I don’t believe that’s a thing though, so for the purpose of my response I will be disregarding death as a factor of how countries organize transportation.
I know more about European urban development than anywhere else so I’ll stick to what I know and use Europe to compare. It may be different for Asia, Africa, the Middle East, South and Central America, etc.
Here we go.
European countries had been populated with developed civilizations hundreds of years before the US. There were well developed cities and roads prior to the invention of automobiles, and they were not developed with cars in mind. The result is that there wasn’t enough room to make big wide roads to accommodate cars.
Trains came first, so some infrastructure that could have been auto centric was already dedicated to rail infrastructure.
European populations were used to living within a confined territory that has already been built out for generations before the car came along. Europeans tend to have a greater sense of shared space, community, and commonwealth; private ownership is less of a priority, and strong/strict government regulation is more common, compared to the US.
Next…
In the US, there were huge swaths of undeveloped land when the car was invented. Henry Ford was an early adopter (some say inventor, I don’t know and don’t want to look it up so we’ll say early adopter) of the assembly line, bringing car ownership within reach of average folks. I can’t remember the exact figures, but Harley-Davidsons were more expensive than a Model T. (Fun fact, both companies started in 1903.)
So you have cars being mass produced immediately upon their inception, they’re useful and flexible and extend people’s sphere of experience, and can even be cheaper than motorcycles, certainly more practical (remeber, roads are more a suggestion for ~50 years after the car was born in most places in the US). They are widely adopted, several other manufacturers join the party, and almost immediately after the invention of the mass produced automobile, the auto industry is a significant part of the economy.
One defining characteristic of America and Americans is individualism. We have all this “freedom” so we make a wide spectrum of choices about everything.
Part of that is private ownership. I am an individual, and as such I have my stuff and it’s not for anyone but me.
Now, after WWII, European economies are recovering, European cities are rebuilding within the same constrained infrastructure that was there before, while the American post war economy is flourishing, manufacturing is strong, and soldiers coming home have access to advantageous home buying programs.
In response to this confluence of events, and due to the vast swaths of undeveloped land, communities sprung up outside of, but adjacent to, urban centers. Suburbs have entered the chat.
To connect them, roads are built, and all these new cars are being manufactured now that raw materials are available again after the war. Suburbs have single family homes, not apartments or the kind of housing blocks of flats common in Europe. There’s a period of suburban sprawl, enabled by and coexisting with, roads and cars.
Now you have people experiencing an apex of private ownership: their own land, home, car. When they’re in their home the Commonwealth is not visible. When they’re in their car they’re using the Commonwealth, but individually, physically separated by steel and glass. These cars are powerful and relative to what came before, comfortable, and technical marvels.
Ok, still with me?
Branding is a thing. Advertising is a thing. Cars advertise a certain identity. Teenagers start taking old cars from the 20s, 30s, and 40s, customizing and modifying them into Hot Rods. A car is more than a car, it’s an extension of self. An exercise of personal agency. AND it’s still a vehicle (pun very much intended) for individual freedom - both freedom of movement and freedom from the Commonwealth.
Now you have this recipe where cars are baked into the DNA of America and Americans. Even though the internal combustion engine wasn’t invented here, America’s coming of age after WWII is inextricably linked to cars.
At this point, its hard to conceive of being American without at least access to a car, if not direct ownership of one. Our urban planning lost out in many ways to the suburban dream, and suburbs are too far flung and disconnected to link via rail. Suburbs then grew into their own population centers, but not in an urban manner with density. The population is all spread out. Public transit isn’t effective without density.
In order to find cheap enough housing and good enough jobs, one has to live many miles away from work, necessitating a car. Suburbs were built for cars, not walking and biking. Many don’t have sidewalks at all. Suburbs have big driveways and big garages, for big cars.
It’s also shockingly easy to get a driver’s license. Because it’s understood that you need a car.
In Europe, there’s less room to accommodate wide streets, driveways, garages. Gas is more expensive. It’s costly and more regulated to get a driver’s license.
SO!
It’s not that there’s something wrong with Americans that makes them addicted to their cars, it’s that there’s something very American about car ownership. So much so that our built environment logistically makes public transit difficult to be efficient, and people have strong relationships with their cars.
That’s my oversimplified but long winded OPINION based on my subjective experience as a former certified Harley-Davidson mechanic, former Tesla mechanic, and son of a 50+ year mass-transit city planner. I love cars and motorcycles. And I also love buses trains and trolleys.