What if...say in November 1912, the Spanish Influenza breaks out and by June 1914, it kills twice the total number of people as it did in OTL. What would happen next? Would World War I still happen?
Exactly. It started in the US, near an Army training camp. Those soldiers carried the virus to Europe where it ran rampant and then from there to the rest of the world and then back to the US. It's spread would have been slower than during the war.