The CDM’s Location table includes physical location fields such as street address, state, zip code, and county. However, there is no field for capturing the country of the subjects.
The Country field will be based on the ISO's 3166-1 vocabulary (https://www.iso.org/obp/ui/#search), which officially designates 2- and 3-character codes for 249 countries. The alpha-3 set, which uses 3-characters, is the suggested version. Assuming alpha-3, then the Country field would only need to be a nullable varchar(3).
For data sets with patient records originating from multiple countries, there is no way to represent this difference in country; you could not stratify an analysis on country or include country as a covariate. We do not have a real-world use case at this time.