The entire planet gets into a war in the early 1900s because some two-bit archduke of something-or-other got shot? WTF? Woah, back up there, Teach; you've got some explaining to do. (And when I read the explanation years later, I still go "WTF?")
Point is, if the cliche is correct then we're doomed to repeat history again and again because there seems to be little effort to explain why things happened. What the hell was the U. S. doing in some dot on the map in Southeast Asia in the 60s? Domino theory? C'mon, I doubt anyone believed that even at the time if a ten-year old version of myself is saying, "how dumb do you think I am?"
But, as you mention, it would seem that there's little enough time to teach the timeline, let alone explain the treaty situation of early 1900s Europe such that WWI makes sense.
Btw I was at the WWI memorial in Kansas City (created just a few years after the war) and they list Darwin as a cause of the war! The leaders of the world had read his "Origin of the Species". It was variously interpreted politically to mean 'the strongest culture will win' and used by the German leadership to justify war. War was natural, it would winnow the nations down to just those worthy of survival, and Germany was the most worthy.
The cause of war is not usually taught. It's the events that led up to war that is. http://en.wikipedia.org/wiki/Events_leading_to_the_attack_on...
1. A timeline where you ought to remember what happened before and after that thing.
2. Objectify events based on causal reasoning presented in the books itself. For example "America got dragged into WWII because of an unprovoked attack by Japan that caused a massive loss of life and military resources"
And the share volume of world history covered in a year or so makes it so hard to do any justice to a topic.