Why do you feel better when you go to Europe, or even to Disneyland? Humans crave walkable neighborhoods. American and Canadian infrastructure is the main reason we have so many mental health problems.
I buy the value of walkable neighborhoods, but it's hard to make this epidemiological claim hold up; Canada and the US have broadly similar infrastructure but sharply different rates of mental illness; similarly, mental illness rates don't appear to track walkability in Europe.
It takes a single search to find many different studies and meta-studies about correlations between noise, air pollution and mental illness, cardiovascular health, life expectancy and others.
I encourage you to look for studies about a metropolitan area near you:
Car traffic is not harmless. Noise is not harmless. It's just that those who contribute the most to pollution anr noise usually don't experience it every day for hours on end, or even during their sleep.
If you prefer esoteric subjects to obvious ones, I'd recommend this study:
https://www.mdpi.com/2073-4433/11/5/467
If you are looking for proofs for the obvious (living at a busy road makes you sick), there are plenty of studies about this subject as well.
Cancer rates rise, IQ drops, life expectancy drops, all in clear correlation to your immediate environment.
As a German, also the pedestrian's and cyclist's utopia that Europe is painted as on US media also sickens me.
It's purely a matter of money and inheritance.
Good luck finding a non-toxic place to live in a big city with an average wage and *without owning a car*.
Possible, but exceptional.