it involves balls
This question has know actual answer because people have different opinions, but I believe it is basketball.
Tenpin bowling is played all over the world. It is most popular in the US and UK, but is very popular in Asian countries as well. It is the most popular indoor sport in the world.
The most popular sport in America is Football.
The second most popular sport would be baseball. Although it is second for most popular SEEN, it is first for the most PLAYED sport.
The NFL and College Football are really popular sports watched in the USA. Football is the most popular spectator sport in the US.