Germany's annexation of Alsace-Lorraine was a source of ongoing resentment by the French. As was France's loss of its status as the dominant land power in Europe. War was not inevitable, but the unresolved issues from the Franco-Prussian war ensured that the two dominant continental powers would be enemies. France's desire to be secure against Germany leads it to form an alliance with Russia, which then puts Germany in a terrible situation of being surrounded by two great powers. You're right, it's not like two people held a grudge for 45 years, but the war made it likely that the two nations would fight each other again.
And then the Treaty of Versailles went on to cause the forced repairations and subsequent hyperinflation and depression in Germany leading to the Nazi takeover and WW2.
An interesting anecdote, France weathered the world depression of the 30s much better than other countries because they kept getting reparation payments from Germany.
When I hear this I think of the main plot of the fantasy book "The Magic of Recluse" [1] where the increase of Order (good) came with the resultant increase in Chaos (evil).
The analogy is that the Allied powers could probably have avoided the post-tranquility strife by not asking for The German Empire could not give.
By creating this imbalance, they fed the very outcome they dreaded (another Great War).
In the Recluse Saga Chaos is not evil, and Order is not good. It is exactly that. Order and Chaos. Albeit most Chaos wizards tend to be evil, and most Order wizards tend to appear more evil. A lot of the heroes in the saga are actually Grey, or those who use a balance between Chaos and Order. Cyador, for example, was a decent empire despite being inherently Chaos.
You essentially argue that the alliamce system caused the WW1 but I don't think that argument works very well. An alliance system alone does not cause war. The questiom is why within a given international situation some people start a war.
The reason the relation did not change was not just Alsace-Lorraine, there are other issues. So I really think it can not be called a root cause of WW1.
I suppose it comes down to whether you're arguing what started the war or what started the world war. Without the alliances, Austria-Hungary would have invaded Serbia and that would have been it.
