Drupal Content Updates Not Visible to Public Without Login Attempt
The Drupal site seems to treat an unauthenticated log in attempt to be an Anonymous User


Correct; an anonymous user is unauthenticated.


  What is the "role" of the viewer of the site before a login attempt is made?


"anonymous user"


  Where is the site content being pulled from to display in browser when the site URL is first loaded?


Either the database or your cache store.


  Where is the site content being pulled from after a login attempt?


Ditto - database or cache, depending on your setup, whether caches have been primed for the particular cache id, etc.

It sounds like you simply have page caching enabled for anonymous users. Clear Drupal's caches and see if the problem persists.