That's absolutely not true. It only became true in the post-war when there was a push for suburban sprawl, lobbied by GM and all the auto industry [0]
> it's pretty safe to bet that she doesn't think that she can live where she does without a car.
"Where there is a will, there is a way", right? The discussion is not even if she can go by without a car, but whether she would want it.
> We can't even manage the political will to build enough housing to keep people off the streets.
Ok, but then don't go around trying to rationalize your bad choices and poor capacity for civic organization. [1]
Don't go around saying "I lived in NYC and I thought I could live without a car, but after I had kids I realized they are not so bad", and please don't go around saying "it can't be done".
Amsterdam and Rotterdam were once also car-centric cities which managed to turn themselves around in less than a generation. There is no inherit limitation in the US that forbids this change to happen. There is no amount of American Exceptionalism that can prevent people from clamoring change. Maybe it won't be done in the US, because people are lazy and not willing to sacrifice their own convenience for some communal benefit, but it's super annoying to always get in these discussions when people try to hide their preferences on external circumstances. North American cities are they way they are by choice.
[0]: How The Auto Industry Carjacked The American Dream (https://www.youtube.com/watch?v=oOttvpjJvAo)
[1]: The Dumbest Excuse for Bad Cities (https://www.youtube.com/watch?v=REni8Oi1QJQ)