Today in the Roman Martyrology we find this entry:
11. Emmetsburgi in Terra Mariae e Civitatibus Foederatis Americae Septemtrionalis, sanctae Elisabeth Annae Seton, quae, vidua effecta, fidem catholicam professa est et puellis instituendis necnon pauperibus pueris alendis cum Sororibus a Caritate Sancti Ioseph, quarum Congregationem fundavit, sollertem dedit operam.
At Emmitsburg in Maryland of the United States of North America, [the feast] of Elizabeth Ann Seton, who, once she was widowed, professed the Catholic faith and gave skillful care with the Sisters of Charity of Saint Joseph, whose Congregation she founded, to the instruction of girls and raising poor boys.
As you work through the Latin of the entry don’t forget that the phrase operam dare is "to bestow care or pains on, to give attention to any thing" and it is constructed with the dative or with ut or ne (= studere). In our entry, we see it is dedit operam … puellis … necnon pueris. So, the writer used the dative option.
We should also remember that the entry says United States of North America, because there is another United States of America, in South America, that is, Brasil.