It's because the banks that issue credit cards have most of the negotiating leverage, and they don't want giant US banks competing on their territory on the payment acceptance side. As a result, you need to use a European bank to accept payments in Europe, a Latin American bank in Latin America, and so on. The payments industry is full of these non-obvious (and unfortunate...) power dynamics.
What's the reasoning behind that restriction? Could you just re-use your backend stack, but use a different data center / machines, that's isolated from the backend of other countries?