When public transit advocates dismiss such inhuman conditions as a non-concern, I can only laugh. The average driver in America will never be shot at in any point in their entire life, but by your own admission inhumane filthy conditions are so common on city buses that you saw all of the above behaviors, excepting only the assault, during a short stay in Paris. I prefer the very infinitesimally small chance of getting into some sort of Mad Max scenario in my car to a 100% chance of encountering disgusting filth on a city bus. Most Americans agree with me. Most people who say they disagree actually have no choice and when they say they prefer the bus they're just coping: https://en.wikipedia.org/wiki/The_Fox_and_the_Grapes
If America had a civil and clean population like Japan, then the situation could be different. Clean city buses would be inoffensive, but that's not the reality we're dealing with. The deranged antisocial population of America is substantial. Maybe you'll say that we should fix that. You bet your ass we should. But until that happens, don't expect people to put up with city buses when they have any other choice. Just because you're okay with wallowing in filth doesn't mean the rest of us should be.