OK, so person a deposits cash, person b in another country withdraws cash. Eventually bank location a will have an excess of cash and bank location b will have

OK, so person a deposits cash, person b in another country withdraws cash. Eventually bank location a will have an excess of cash and bank location b will have a shortage of cash. How do you square that? Now think about the fact that 25% of el Salvador's GDP is remittances from the US. Country wide, banks have a shortage of cash deposits every Friday. Bank location a will need to eventually ship that cash to bank location b, and maintain a channel to keep the money flowing. It's not that simple, if it were that simple that's how banks would do it. There are logistics involved.