Generally, cash doesn't do anything. It just sits there, in notes or as numbers in a bank account.
All the smarts are in the banking institutions, in the payment processors, etc. There's the raw account qties, then there's an independent system atop it that implements atomicity, then there's an independent system above that that implements merchant transactions, or financial products etc, and then more independent layers atop those.
Each layer can be used on different underlying layers, as they're agnostic to the actual thing being transacted. Visa doesn't really care whether you're paying in EUR or USD, as long as both sides match (and it's the bank's job to make them match in most cases). An international bank implements term deposits or loans etc essentially the same way no matter what country they're in (regulatory requirements aside)
