Setting the supportedCountries property on an Apple Pay payment only works when using ApplePaySession, not when using W3C Payment Request. Only the latter one sets supportedCountries on PKPaymentRequest, and filters cards by issuer country, as can be reproduced on https://applepaydemo.apple.com.
rdar://113557607
Pull request: https://github.com/WebKit/WebKit/pull/16586
Committed 266829@main (e5afaf96365a): <https://commits.webkit.org/266829@main> Reviewed commits have been landed. Closing PR #16586 and removing active labels.