No, not at the brink.
I have studied to much history to think that.
That's really difficult to imagine.
Some of my friends seriously believe that something 'ODD' will occur, some type of "wild card" event, out of the sky blue, utterly unexpected will occur - which will radicalize the population into separate groups who then fight eachother, on a large scale like outright civil war, but I total disagree.
Certainly, as you suggest, historically speaking, there would have to be many many many more factors at work to bring a huge nation, comprised of so many different groups & interests, to the ACTUAL brink of civil war.