For a better treatment, I turned to The Chicago Manual of Style (sixteenth edition), used by the vast majority of publishers of American English books. It says

For a better treatment, I turned to The Chicago Manual of Style (sixteenth edition), used by the vast majority of publishers of American English books. It says in Section 7.19 to omit the s "...when the name of a place or an organization or a publication (or the last element in the name) is a plural form ending in s, such as the United States, even though the entity is singular." And cites these as examples: the United States' role in international law Highland Hills' late mayor Callaway Gardens' former curator the National Academy of Sciences' new policy