I’m trying to change the default billing country in the PayPal payment form with no luck.

I’m using this link as reference and have tried different combinations of parameters already.
https://developer.paypal.com/docs/api/orders/v2/#orders_create

Here is my code so far.

var request = new CreateOrderRequest
{
    intent = "CAPTURE",
    purchase_units = new List<PurchaseUnit>
    {
        new()
        {
            reference_id = reference,
            amount = new Amount
            {
                currency_code = currency,
                value = value
            }
        }
    },
    payment_source = new PaymentSource
    {
        card = new Card
        {
            billing_address = new Address
            {
                country_code = "GB",
            }
        }
    }
};

I passed the country code as “GB” to change the default billing country in the PayPal form.

I expect it to change to United Kingdom, but the default country is still showing US.