The answer is that a secret ritual is performed with each child in the USA sometime between the ages of 12 and 16. During this ritual the child is taken to a cobweby vault wherein lie the sacred books of American English. The child is given several minutes to choose one or more stylistic identities that they will then use for most of their adult lives. The ritual is solemn and the secrets of the vault are well guarded.
I have recently come into position of a partial list of the tittles of the vault’s books. The information was hidden where no-one could have dreamed anyone would look for any useful information. There is a rumor that more complete lists are hidden in the footnotes of many English department dissertations, but that is just too well hidden even for me.
The Great Books of American English:
Tautologicon –Quite a tome for such a large book.
Paroemicon - a beautiful bespeckled book bearing bunches of bangles.
Acyrologicon – A great big boob.
Battologicon – A really really really great book.
Cacozelicon – Whose parchment is as white as the syphilitic thighs of geriatric cadavers.
Soraisicon – Book good much read should you.
Parelcinon - quite a jello useful book.
Parrhesicon – I’m so sorry for even mentioning this book.
Bits and pieces of these books have been smuggled out over the ages. Eventually this knowledge will be available for all, and the cabal of the American English priesthood will be shattered.