Watching American football broadcasts I've noticed (or think I have) the commentators are very carefull to always call the object "football", never just "ball". That is obviously correct, as it is not a ball, even though it surely would be simple and practical to call it such. Is this a consensus/decision/rule or have I just missed the times they call it a ball? 

....also known as the pig skin.

Of course, pig has a whole different meaning in here
 
 
IIRC, I've heard some commentators state "the ball is on 5 yard line, 1st down and goal to go" etc...

The ball is on the [ insert number ] yardline. They say it all the time. Used frequently in other contexts too. Keep watching. 

Reminds me of a sign at the rugby club where my dad played:  "Rugby is a game played by men with odd-shaped balls." 
Football applies too.

Kalle Rantaaho
Watching American football broadcasts I've noticed (or think I have) the commentators are very carefull to always call the object "football", never just "ball". That is obviously correct, as it is not a ball, even though it surely would be simple and practical to call it such. Is this a consensus/decision/rule or have I just missed the times they call it a ball? 

AND, it's not a "football" either! The game is played by carrying the ball ... not kicking it! The kicking part of it is to get rid of the ball to the other team.
 
The US National Men's team (soccer) could use learning from that, I think ... it might help their defense! 

Well...it's also to make 3 point FG's and 1 point PAT's.  Not nearly as often as carrying and throwing..but yeah

One of my all time favorite George Carlin routines!
 

 
 

Moshkito
 
AND, it's not a "football" either! The game is played by carrying the ball ... not kicking it! The kicking part of it is to get rid of the ball to the other team.
 
The US National Men's team (soccer) could use learning from that, I think ... it might help their defense! 

I've always thought it should be called "pitball". The object is most often transported under your arm or about.

I see this argument a lot.