As has often been stated, football is like war.
The differences between American football and the-rest-of-the-world football are directly related to the methods in which war is carried out by America vs the rest of the world.
In world football, all you need is a pair of shoes, shorts, and a ball. Anybody can play, as long as they can run and kick.
In American football, you go heavily armored, and you can’t play without the proper equipment.
In world football, injuries happen, but they typically aren’t too serious.
In American football, the heavy armor allows players to avoid minor injury, but allows play to be even more violent, leading to more severe injury.
In world football, the rules are simple, the strategies straightforward. The players have different positions, but they all do pretty much the same thing, and any player can probably play any position.
In American football, the rules are complex and the strategies infinitely varied. Each position is highly specialized, and it’s unlikely that a player will do well in a position he hasn’t trained for.
In world football, play is fluid and continuous.
In American football, the action stops whenever a few yards of territory have been gained.
In world football, it is possible for the game to end with neither side having achieved their goal.
In American football, the game must go on until one side has delivered a crushing defeat to its adversaries.
In world football, the supporters of the team are mad, mindless, screaming partisan fanatics, who will take to the streets themselves if the game doesn’t favor their team.
In American football… uh, okay, so they do have that in common.