I think Kansas was reported as the origin?
Kansas was one of the first known cases of the flu in our troops at home. The basis for the Chinese origin is that the Brits were using Chinese to fill in behind the men who'd left for the war. They were originally shipped from China, around Africa, and to England. But the Brits needed a faster way. So the came from China to Canada and across Canada to the Atlantic. Some were known to have been sick when leaving China. Theory is that it spread from these folks into North America as they were shipped across.
https://www.history.com/news/china-epicenter-of-1918-flu-pandemic-historian-says
As an aside, we also have the plague in the southwestern U.S. Once again the origin was China. It came from the rats that infested the Chinese trading ships that docked in San Francisco and Los Angeles in the late 1800s and early 1900s. The plague made it from those places into northern New Mexico, northern Arizona, southern Colorado, California and western Nevada. We usually see a case or two annually in New Mexico. Treated easily with antibiotics if caught quick enough.