给定一个文本，将其中的所有"soccer"替换为"football"。如果"soccer"前面有“American”，则用“American football”替换掉"soccer"。



Soccer is the most popular sport in the world, but American soccer is not as popular as American football in the United States.
Football is the most popular sport in the world, but American football is more popular than soccer in the United States.