The alliances system meant that a local conflict could easily result into an intimidating global one. The overall cause of World War was the assassination of Archduke Franz Ferdinand. Nationalism was a great cause of World War one because of countries being greedy and not negotiating.
Your welcome I don't know if that helped. But yea.
Without a doubt, the United States has never really lived up to the ideals of the Declaration. Historians, myself included, are quick to point out that Thomas Jefferson enslaved several hundred human beings when he crafted the Declaration.