[ChemicalWarfare]

Well, they aren't THAT late :) Visa, for example launched something like this just few months back.

I'm also not sure what kind of impact these APIs have in the "real world", I'd venture to guess vast majority of the merchants is sticking with one-stop-shop payment processors instead of switching to point-to-point integrations with card networks.

[WhitneyLand]

Stripe was founded in 2011. Regardless of whether or not AmEx sees Stripe as a competitor/threat, they wasted 5 years not building out similar tech after the blueprint was laid out at their feet.

[ChemicalWarfare]

Payment processors like First Data and Cybersource have had these types of APIs available to their merchants since the late 90s actually.

Since you mentioned Stripe - they are actually one of the cheapest options to process AmEx, depending on the volumes and CC/Debit breakdown even cheaper then going through AmEx directly in some cases.

So again this is more of a business driver vs. the available tech thing.