Why can't I apply an Apple Card?

How to apply for Apple Card - Apple Support

• Be 18 years or older, depending on where you live.
• Be a U.S. citizen or a lawful U.S. resident with a valid, physical U.S. address that is not a P.O. Box. You can also use a military address.
• Own a compatible iPhone with the latest iOS version.1
• Use two-factor authentication with your Apple ID.
• Sign in to iCloud with your Apple ID.
• If you have a freeze on your credit report, you need to temporarily lift the freeze to apply for Apple Card. Learn how to lift your credit freeze with TransUnion here.
• You might need to verify your identity with a Driver license or State-issued photo ID.

Additionally the Region on your iPhone also needs to be set to the U.S. Settings->General->Language & Region->Region

There's some good info in this thread already. I would just add that you need to be running at least iOS 12.4 to apply for Apple Card. If you're running the iOS 13 beta, you'll also be able to join.

[Link Edited by Moderator]

It’s only available in the US.

Do you live in the US? Are you over the age of 18? Are you running the latest version of iOS?