The State field that appears underneath the Billing Information section on forms cannot be disabled, as it is hard-coded into the software.  We recently made a change where the Province field could be added to the form and State is no longer a required field.

Any donors, participants, etc., will not have to enter anything into the State field under Billing Information in order to allow for their transactions to go through.

However, for people that Register a Family, the State is still a required field.  In this case Chat with Support and reference this article.