They only called it the "Spanish Flu", because as a neutral during WWI, Spain was one of the few countries that didn't censor reports of cases in their country, thus the only reports people heard about were the cases in Spain. There is speculation that there were so many cases in Germany, it was a factor in them losing the war.
The reason Germany/Austria-Hungary lost was that the US entered the war. Obviously the flu would have impacted all combatants. It wouldn't be surprising to learn that the 1916/1917 hit the Russians as well, and helped push that regime off the cliff and out of the war.
There’s been the theory that the Spanish Flu originated in western Kansas.
More recent is the theory that Chinese laborers brought it from China to Canada. Canada entered the war long before we did and they had a labor shortage that had them importing Chinese help.