I think "Social Media" is the wrong description, or only part of the issue. It is really just information and it's availability. Social Media is part of it, but just one part.
I remember reading a book about Chuck Yeager in the early 80's (May have been "The Right Stuff"), but in it he talked about growing up in Appalachia. He talked about kids not having shoes and he and his friends being poor....but that he never KNEW he was poor until he left and joined the military. There was the one "rich" family who owned the general store, but everyone else was the same. And that "rich" family was the pinnacle of what rich could be. So he wasn't poor, he was just the same as everyone else and had what everyone else had. They didn't really know they could or should want anything more.
With the overwhelming information, media shows/clips, and social media (much of which is exaggerated or made up to drive interest), people can now measure their happiness not based on a smaller world view, but on the view of what they have in relationship to everyone else in the world.