Allow pre-filling customer country in Checkout API?

I’m implementing purchasing power parity (PPP) pricing by offering location-based discounts to customers in lower-income countries through single-use discount codes.

To prevent misuse, I need to ensure that discounted purchases can only be completed by customers located in the intended country.

Specifically, I need a way to pass an allowed-country(or countries) restriction when creating a checkout session through the API.