I think when you look at the history of the United States you have your answer, though I believe it is in a constant state of metamorphosis. Four hundred years ago America represented a chance for many to find a new beginning. When colonies were established people ventured to the new world to what they had hoped to be a place to call home. When they arrived, many found what they were looking for while others found that they still need to keep looking. Because there was a lot of new space they were able to carve out a place and adapt it to what they wanted. When they had a common cause they united behind it. However, once the goal was achieved then their differences and prejudices divide them.
The history of our country shows this to be true. When time and space separated us, it was easier to live together as one nation because regional divides allowed for like minded to congregate and be as they choose to be without the outside viewing and judging. Today that is no longer available.
Twitter and Facebook, and social networking in general provide a platform to voice ones views about anything. That same platform is a window of what is happening in the world in real time. When a horrendous act of injustice is witnessed the participants on the internet can unite in a common cause. But our differences continue to divide us.
Unfortunately the larger providers of information still pick and choose what the majority of us get to see. Those in power have huge coffers of money to spin events with their own slant, whether it is true or not.
As time passes, however, more people will see what is real and what is spin. It won't happen over night because the spin masters have been at it a long time, but when a public figure continues to demonstrate incompetence, lies, half truths, or inaccurate spin more people will see through the presented veil. Lincoln said it best, "You can fool some of the people all of the time, and all of the people some of the time, but you can not fool all of the people all of the time ".
We will always have differences of opinions, but as long as we can agree to disagree, then I see social media as being a good thing that will let even more people be able to participate. We will become more tolerant of our melting pot and hopefully more interested in incorporating our differences then in excluding them. But then I am an idealist.