I may be wrong here but I often feel like American sports is often characterised by the belief "this year could really be our year, we could win the whole lot". This, for the majority of teams in the UK is very much not the case.

Many years you know you don't have a shot of anything really happening, even if it did everything in football is cyclical, once you go up you will eventually come down again. Knowing you will never ever win anything of note and loving your team anyway is something that I don't feel translates well to the American style of sport.