We have the best form of government outside of a benevolent dictatorship or kingdom. Unfortunately it requires a free honest unbiased press along with an informed knowing intelligent population. Unfortunately we are not all the same ( think normal distribution curve of any human characteristic ). There in lies the problem. In the long run I believe all types of government are doomed to failure.Small family groups don't always get along for the same above reasons. The larger the size the more problems and the greater the damage.
It also requires congressional and high court term limits and the government practicing what it preaches against internal wrongdoers. I don't disagree though with your deeper point that we're all headed back to the jungle in some form or fashion as we instinctually seem to live by that code for better or worse (usually worse).