VSauce recently had a really good video about awkwardness that touched on this topic briefly.
Protagonist Syndrome: A particular brand of narcissism in which a person views him/herself as the main character in a work of fiction. Everything this person does all fits into a narrative, this person has ambitions, dreams and obstacles all leading up to a goal. But what are those obstacles? Other people, obviously. Friends are all supporting characters, strangers are background characters, and the villains are those who get on your nerves.
Everything bad that happens to you is a result of other peoples' stupidity, negligence, or outright malevolence. You can never be wrong because you're the main character, and constantly fighting the persecution that the world throws at you!
So basically, every single other person on Earth is reduced to a one-dimensional piece of scenery, a supporting character at best or an obstacle at worst, neglecting the fact that all of those people are leading lives every bit as full and rich as your own.
This worldview appears to be incredibly pervasive, and I know I experienced it in my teenage years before I found a girlfriend. Those who keep it well into their adulthood, though, tend to be annoying to talk with at best, or at worst, hideously selfish.
These are the people with persecution complexes, who defend their actions even when just about everyone has turned against them (usually for good reason). Sometimes these people are just savvy enough to find their way into positions of power.
So yeah, I'm sure that human selfishness is pretty much the root of all problems humans face.
I've discussed before that a good cure for humanity's problems would be a mind link that all humans possess. Through this they would step into the brain of someone they were interacting with as a spectator and experience the collective thoughts and feelings of everyone else as if they were their own.
This would have a wonderful effect of ushering in a new era of understanding and cooperation. People could still act as individuals, but knowing what others think and feel would greatly discourage them from being selfish. The barriers between humans are possibly the biggest barriers of all, break them and we can become truly enlightened.