american football is slightly similar only
The game of rugby is most similar to the American game of football. In both games there is a ball, running with the ball, and kicking the ball. Rugby is played in more nations than is American style football. Rugby is, however, a sport played in most US colleges & universities.
American football is the only American sport that has similarities with Rugby. However, these are very few. The Game of Rugby has however seen a massive increase in popularity with the US over the past 2 years
rugby
Ki-o-rahi is a Maori sport quite similar to rugby
Rugby
American football or rugby
Rugby/American football.
The British Lions, now known as the British and Irish Lions, play rugby union football.
The sport Rugby League is the same as in the USA. The competition however is called; American National Rugby League
Rugby Football
This is a bit of a complicated question, based on nationality... If you are from the USA, football is a version of the British sport Rugby, invented at Rugby School (at Rugby.) If you are British, football has evolved over time from a medieval sport in which a pig's stomach was blown up and kicked around.
Soccer --> Rugby --> American Football