Outside a handful of markets, card-only checkout is a self-inflicted conversion problem. Brazilian users want PIX. Indian users want UPI. Dutch users want iDEAL. German users want SEPA. The conversion lift from adding the right regional rail is rarely under 10% and frequently above 30%.
Authorization rates tell the story
Card authorization rates outside their home markets are quietly terrible. International cards in Brazil sit in the high 60s. Domestic PIX in the same market clears at over 95%. The conversion math is not subtle.
Pay attention to what happens on the second attempt. Card retries are expensive and frequently degrade further. Regional rails either work on the first try or fail in ways the user can correct on the spot.
What to build first
Start with the regional rail that covers the majority of your local volume. Do not try to build a rail orchestrator before you have one rail working well. The rail orchestrator is what you build when you have three or more.
Plan for the reconciliation work. Regional rails do not settle the way cards do. Your finance system will need new line items for each rail, and the daily three-way reconciliation that keeps gateway, ledger, and bank in sync is not optional.