Even before the arrival of social media, the mass media was feeding people stories about the world which made it look far more dangerous than it actually was. S

Even before the arrival of social media, the mass media was feeding people stories about the world which made it look far more dangerous than it actually was. So media isn't the reason. The reason is that the majority political philosophy in the US has shifted from libertarianism/classical liberalism to progressivism. The libertarian point of view is that people generally should be free to go about their own business in the manner they see fit. The progressive point of view is that we have a collective responsibility to police the wrongdoing of other people and fix it, using state power if necessary. In the video where the guy goes off at the mother for leaving her kid in the car, you can see the progressive power dynamic in play immediately. The guy thinks she's doing something wrong so he gets involved. (Who is he? Doesn't matter. It's everyone's job to right wrongs.) It takes maybe 15 seconds before someone mentions the police, because the only way such intrusive activism works is when a higher power (can be state, law, society, science, God, whatever) is used to identify and enforce a definition of what's right. Even though the activist doesn't explicitly threaten to call the cops, during the confrontation they are mentioned constantly because the threat of state power is the only reason the mother even has to give this guy the time of day. If you want to go a level deeper and ask why this political shift has occurred, it's likely that one contributing factor is urbanization which been underway in the US for some time--historically densely populated cities tend to be more authoritarian than rural areas because a crazy person can do more damage in a dense city (you don't see mass shootings happening in cornfields).