For me both soccer and wrestling were the most difficult in terms of cardio for me. Completely different kinds of cardio, you will be amazed how tiring grappling is. Even just for 3-5 minutes. In soccer there is no real breaks in action so when playing mid field you just run your ass off at all times.
Both extremely tiring sports. But just like those two sports are different, so is American Football. It's alot of full sprint explosive plays combined with pushing people around. It's exhausting as well. But it's more about short explosive burst.