I had not thought of it that way - car-dependent places being poorer. Part of the reason this is not so obvious is that a car is a status symbol and people do like their nice rides and to feel special in their pride and joy car.
But it stands to reason that if all of your out-goings are paying for the motor then you are going to have less money to spend or invest in other things. If someone has a fancy car it may be leased for x amount per month with restrictions on miles driven, the financing being fairly scammy for the buyer and the auto-maker. Yet we see the gleaming motorcar and assume 'that person must be rich' (rather than pity them for their apparent status anxiety).
We don't see that person on a bicycle and think 'they must be rich', envying them for not outlaying $$$ a month to keep a tin box on the road belching poisons. Instead we are more likely to wonder what is wrong with them. In the last century you would possibly wonder if they got nicked for drink driving and their punishment was to be relegated to two wheels. Luckily attitudes have improved in that respect.
It is the same with houses. The person that rents might have debts but the person with the million dollar mansion and some type of interest only mortgage really does have a million dollars of debt hanging around their neck. Yet we perceive them to be rich. By this logic the homeless guy in the park is richer than all the neighbours beholden to banks rentseeking them with their mortgage products for 25 year periods.
The people who are actually rich as they have inherited the land are dismissive of the nouveau rich, maybe they know the truth at these folk haven't actually got tangible wealth, just big debts to banks and wannabee status anxiety. You can find landed-gentry types wearing the same coat for thirty years and driving round in cars approaching that age, beaten up and full of dog hairs. They might have bought that ancient Volvo new, no finance needed. They might also use it to buy very fine food and drink from the posh supermarket. They don't have status problems like the people in fancy cars do.
America is different to Europe in this aspect, partly because there is this idea that America is the land of freedom and opportunity, in Europe people kind of know their place and don't feel ashamed to do a regular job. In America you have to be a rockstar or die trying. Sense of community doesn't fill the void when life is one of suburban sprawl. In a walkable community you should be able to say hello to a few people just going about your business, a wave and a smile shared with that old guy you see walking his dog every day does give you some sense of belonging in your (little) world. You might grumble about the guy and how his dog walks so slowly with no road sense whatsoever but that passing acknowledgement of existence is a community bond, the smile is real. Driving some shiny behemoth of a vehicle gives you none of that, sure you can wave from the window and hoot your horn but it is still a little mobile prison cell of sorts. You can't actually stop and chat. Sure you are off to see more important, higher status people that have better convo than the doddery neighbour with the dog but you are also spiritually a bit poorer for not being part of a local, walkable community.