What has driven alienation in America? You could make the case for hyper-individualism and that plays a big part. The way our cities are designed also plays a role - mostly they're designed around the automobile which doesn't afford us opportunities to run into people we might know as we walk around. Cars are privacy bubbles that allow us to be isolated as we travel around. Look at a European city. There are often people just chatting on a corner or in a piazza - interaction happens much more often in those contexts because those cities tend to be set up in such a way to allow it to happen.
Finally, I think the American fetishization (for lack of a better word) of work plays a role. We Americans tend to define ourselves by the work we do to a larger degree than people in many other parts of the world.
Given the isolation that was already there in American culture, along comes social media and initially it kind of looked like it was going to help be an antidote to that isolation - I think a lot of folks wanted out of the isolation and thought that was going to be a way out. But it ends up often making it even worse - and definitely exacerbates the division between tribal groups. Our alienation causes us to want to identify with these tribal groups for a feeling of belonging and these tribes end up "shitting on" other tribes not aligned with them.