Pipeline or Automation Help Converting State Names to abbreviations

I'm a little confused here. You are saying you are using the default address field but in my experience, and even just testing it now, the default address field has a dropdown for states. You cannot enter it yourself you must select one of the available options that is already there.

If this is not the default address field I have some ideas for what you could do. Even if it is the default field you could have a formula field on the side calculating the abbreviation of the states.