1. SAP Help Portal
Implementing and Managing Recruiting
"Country/Region-Specific Fields for Job Application": "You can configure country/region-specific fields for a job application so that candidates are asked to provide different information based on the location of the job they're applying for. The country/region of the job requisition determines which fields appear on the job application." This official documentation explicitly states that the job requisition's country is the trigger.
2. SAP Help Portal
Implementing and Managing Recruiting
"Configuring Job Application XML Template": The guide details how to use the country attribute within field-definition overrides in the Application XML. It states
"To make a field country/region-specific
add the country attribute to the field-definition tag... The value of the country attribute must be a valid two-letter ISO country code." This confirms the mechanism is tied to the job requisition's country value matching this attribute.