Bulk actions validation

I need to design a solution in which a User can map fields from our App to an Integration. And actually, this bit is already prepared. The problem occurs in the fields. Let's say my App has a field Nationality, in which the possible answers are: "Spain, France, Italy". But the Integration app takes only "Spain, Uruguay, Brazil". Whereas it's pretty easy for a single situation. How can I handle it for bulk actions?