Americans seem very "fighty" compared to people from many other countries. You just have to say something that could be construed as liberal (the American kind) or conservative, too politically correct or incorrect, or mention you ride a bicycle or have an outdoor cat, to set some people off. With some Americans having a conversation is like navigating a minefield, especially those who have very little understanding of the rest of the world and reads everything you say into an American context, language barriers and all.
I love talking politics, and have had pleasant conversations with all kinds of people but I have learned from experience to just not bother with Americans, unless they're the very curious and open kind.
If anything it's the car-dependent infrastructure that is ableist, as many people with disabilities cannot drive. I can't, and if I didn't live in a place where alternative modes of transport were a thing, I would either be stuck at home, or have to waste money on buying a specially made car.
Far from all disabled people use wheelchairs or have mobility issues. Some have problems with their sight, concentration, fine motor skills etc. which prevent them from driving safely. Even if you cannot walk or ride a bike, and have trouble getting on/off public transport by yourself, living in an environment that is walkable and bikeable usually means that it is also easier/safer to get around in a wheelchair or on a moped.