Is that a Stripe screen? Set up american style to reduce friction, not supporting 3d secure, which means european credit cards will deny by default?

Stripe supports 3d secure and has for years. https://stripe.com/en-ca/guides/3d-secure-2

Heh. No it doesn't because they require their users to treat it manually and as a consequence a lot of americans don't.

Example 1 that is definitely going through Stripe: Ars Technica.

Example 2 that I don't know what is going through: Asimov's Magazine.

In the race for no friction, they add friction for EU users.

Fineprint says it's Stripe. My (european) credit card worked fine.