Because no other nation really goes by their acronyms, besides the UK and the USA?
Also, do you get annoyed when Australia does their "Aussie Aussie Aussie, Oi Oi Oi"?
Again at least they get a little rhythm to it. It's not great but the U-S-A is easily the weakest. As a Canadian I didn't realize how sad ours were either until I went to a world cup.