If the state_or_province value is longer than two characters the FedEx API will return this error:
The length of the destination state or province code exceeds the limit of 2 characters. Please update and try again. (Code RECIPIENT.ADDRESSSTATEORPROVINCECODE.MAXCHAREXCEEDED)
This is because some countries use three letter characters for some state values, e.g. Queensland, Australia's short code is "QLD".
It would be worth truncating the state_or_province value to two characters before sending it.