Parag Khanna provides a nice analogy between 2011 and the 13th century. (Not the 12th, as he gives it; not with Marco Polo and Ibn Battuta.) He leaves out a lot: the role of religion in particular and the Crusades.
Things started breaking up in Europe in the 13th century. Partly it was an attempt, in France, anyway, to bring the country under the king, but it took a religious cast in an attempt to exterminate heretics in the south. In fact, things came apart so badly that by the 14th century, European society was in tatters and plague-ridden. And the Templars, heroes of the Crusades, were found to be corrupt and were dissolved, the leaders burned at the stake.
One of my hobbyhorses; lots more to say, but no time just now.
Parzival, by Wolfram of Eschenbach
A Distant Mirror, by Barbara Tuchman