In summary, by the end of the 19th Century, the French so loathed the Germans for their humiliation in the Franco-Prussian War that after nine hundred years, they make a treaty of friendship with the British.
All of the European powers looked askance at the upstart Americans who are raking it in economically without the divine guidance of a king, and as a result, all those Royals have given up power to elected representatives in order to maintain their way of life -- you know, living like royalty.
There remained a bunch of crazy leftists who actually believed that insane economic theory crap spouted by Karl Marks and Frederik Engels. Far left anarchists believed they could bring on a perfect society by killing political leaders, especially kings.
Now the Austrian Empire is by this time is a frail and wasting empire run by a weak and inbred family. Disgruntled people throughout the edges of the Empire are in a mild state of revolt. One leftist knucklehead murders the Archduke of Austria and his wife. That assassination will lead to the deaths of 80-100 million people. Damn leftists.
The treaties kick in.
Austria declares war on Serbia. Russia declares war on Austria. Germany declares war on Russia. France declares war on Germany. Germany declares war on France. Great Britain declares war on Germany. Turkey wants some of those Russian Black Sea territories so they declare war on Russia. No one cares much. The Americans are like, how can we make some money out of this situation?
What followed was four years of unmitigated hell. It was war at its most evil. Modern weapons against 19th Century tactics. Poison gas, tanks, aircraft -- all new advances in warfare entered the scene. The Germans unleashed the most evil weapon of all; they sent Lenin and Trotsky to Russia. The Germans considered Vladimir Lenin so awful, so terrifying, they kept him in a sealed, locked train car until they released him inside Russian borders. That evilness accounted for millions of additional deaths in the 20th Century.
Eventually, the French reminded the Americans about their aid in back during the Revolution, and the Americans stepped in on the side of the French and English and Russians. The Germans surrendered and the French remembered how humiliated they were by the Prussians in the Franco-Prussian War. They demanded such harsh terms on the Germans that an entire generation would suffer. These harsh terms would, more than anything, lead to WWII.
