1. The development time is relatively short. It is only in recent decades that the NFL has become the first sport in the United States. Before that, it has always been the monopoly of the MBL family, and now the influence of baseball is still not small. Baseball can't be popularized all over the world, but it can only affect some countries such as Japan, South Korea and Central America, let alone American football?

2. American football is only a branch of rugby. Besides American football, there are English, Canadian and Australian football. In those countries with a mass base of rugby, rugby is obviously more popular, and American football is difficult to compete with it.

3. The rules of American football are too complicated and the threshold of into the pit is too high. Football, basketball and volleyball, even amateurs, can generally understand the basic rules as long as they have watched two games; American football, on the other hand, doesn't. What about advancing yards, three attacks, and switching between offense and defense, a small white man may not be able to understand it after watching 1 games. Moreover, players are still wearing helmets and can't even look at their faces. Basically, they just give up, which is similar to baseball and cricket, so they are not popular.

4. The participation cost is too high. American football has a fierce physical collision, which is dangerous to some extent, and the equipment is expensive. Even in the United States, the participation is quite limited, not to mention other countries. If a sport cannot be participated by the whole people, it is destined to be a minority sport, and so is ice hockey.

5. The NFL season is too short and there are too few games. A team in the five major European football leagues has nearly 5 games in a season, 82 in the NBA regular season and more than 14 in MLB a year. In contrast, the NFL has only 2 games in a year with playoffs in the regular season, which is too few to compete with other sports in the international broadcast market. This is also an important reason why the NFL can't be promoted globally like the NBA. In fact, the NFL has been trying to increase the number of games in recent years, but the players' union has not done it, and the two sides have never been able to talk about it.

to sum up, it is still a long time before American football is popularized all over the world.