The Spanish Flu starting in Kansas is something of a mangled meme.
The virus starting in Kansas was a result of historical forensic work by a historian and an author in 2003/2004. And it's accurate that the first cases reported were in a military base in Kansas in 1918.
However more recent epidemiological data indicates that the virus likely began in China in 1915. Telling is it's modern day identification as an H1N1 virus, with an origin in birds and it being related to viruses endemic to China. It was brought to North America via Canada by Chinese laborers in 1917. Samples of the virus taken from US soldiers in early 1918 match those taken from Chinese victims in 1917. The subsequent spread to Boston and the East Coast was brought on by returning troops from Europe from World War I.
Sources:
https://www.jstor.org/stable/3401475?seq=1
https://www.nationalgeographic.com/n...cience-health/