@Paul_s ISO 3166-1 defines 3 sets of country codes. NetSuite fields that have “Country Code” in the name use the 2-character code (ISO 3166-1 alpha-2). In a Transaction, the Shipping Address is exposed as a set of first-order fields and a joined record. In the dropdown field list, the country code can there be found in two place: as

Shipping Country Code

and through the join at the bottom of the list,

Shipping Address Fields …

. In a formula (as in SuiteScript), these are

shipcountrycode

and

shippingaddress.countrycode

.