France, Italy, and the Balkan allies in the Entente had all surrendered to Germany by 1919.This led to The Treaty of Versailles which radically changed the landscape of Europe. The US never joined World War I due to Germany revoking its policy of unrestricted submarine warfare. There is an extensive timeline on the Kaiserreich wiki which explains major events in detail until 1936, which is the year the mod starts. The timeline of the Kaiserreich universe remains consistent with the normal timeline, until January 8, 1917.
The mod takes place in an alternative universe, where Germany had won World War I.