The USA entered WWI in 1917, against the Germans, as the German military strategy was beginning to fail against the French and British. As the US troops began to arrive in Europe, the Germans suffered a series of military defeats. Meanwhile, the Ottomans (Germany's ally) were also failing in their invasion of Armenia and Georgia. The Germany military, faced with certain defeat, and heavily infected with Spanish Flu, began to mutiny against their leadership and the Kaiser abdicated the throne and then immediately fled to the Netherlands. The new government that took over was eager to surrender to the USA, hoping that they could negotiate better terms than with the French or British. Bulgaria collapsed, and then Austria-Hungary completely broke apart as a nation, and the Ottoman Empire came to an end as it was no longer defensible against so many enemies. WWII was an entirely different story as Hitler killed himself just before the Soviets took Berlin by force, and Mussolini was executed by his own people. The war ended in Europe, but continued for some time in the Pacific until the USA dropped two nuclear bombs in southern Japan just as the Soviet army took northern Japan by force.

The US getting involved brought about the end of both wars.