It’s important to note that the course of the war had several important variables, which made all the difference in the world.
1. It was the last war of the monarchs. Under the brilliant leadership of Otto Von Bismarck, Germany had unified, and whereas before it was sneered at by Europe as a group of agrarian peasants, it had come together as a power in Europe.
This was not appreciated by the other powers, especially France, lead by the egotistical buffoon Napoleon III, who had been elected president, then arranged a coup so he would be declared Emperor. After foolishly challenging President Grant (and his Union Army) in Mexico, he decided to show the Germans who was boss.
With a little trickery, he was snookered into declaring war and invading Germany with an unprepared army, who met him with a prepared army and quickly deposed him. But then, against the advice of Bismarck, the German Emperor Wilhelm II was persuaded to take a piece of France as punishment, which enraged the French against the Germans.
2) Before the war, half of Europe was making treaties with each other; as was the other half, setting up two competing mutual defense pacts. Then everybody started building battleships like there was no tomorrow.
3) The US was set to be a neutral power, but it had a lot of connections with both Britain and Germany. But Britain had something Germany did not, an undersea cable to the US, which only conveyed the British point of view, as well as a lot of propaganda against the Germans.
This wasn’t helped by German ignorance of the US, especially when they asked Mexico for an alliance against the US (The Zimmermann Telegram), which was intercepted by the British, who let the Americans know.
4) Last but not least was US president Woodrow Wilson, a charmingly progressive combination of ignorance and arrogance, self-importance and racism, and who was surrounded by a dense cabal of like minded Democrats.
Yup. The Ems Dispatch. Only the Frogs would declare war because they felt insulted.