From a brief read at Wikipedia, American, European (British) football and rugby are both descended from the same sport, and the unique American rules were codified in the late 19th century. Can we make the British rules be accepted around that time? If so, how would the sport develop?
Would we see a European-style league system with promotion and relegation and a separate cup elimination tournament, or would a playoff system be used? For that matter, would there be seperate leagues for college and pro football, like in OTL?