> You could argue that your VISA, MasterCard, or Amex card is a private "currency" with a fixed exchange rate 1:1 with the card's issuance currency. By offering

> You could argue that your VISA, MasterCard, or Amex card is a private "currency" with a fixed exchange rate 1:1 with the card's issuance currency. By offering you a line of credit on the card, they've "printed" their own private currency I don't think this really flies, the credit is paid, denominated, and collected in USD it's not separate in any useful or meaningful sense. They can't pay out more to merchants than they have in their accounts/credit lines.