As a South African living in the U.S. I can agree that U.S. has many convenient payment products but they aren’t really unified bank-to-bank systems.
An ACH transfer here is more a batch system rather than a true real-time payment system. I’ve seen somewhat a same day ACH but usually it operates around a processing window.
Since the SA banking system is not based around ACH, checks, credit cards etc it sort of helped it leapfrog some legacy systems.
Because of these different development paths South Africa have more integrated real-time payment infrastructure and the U.S. is recently transitioning toward a true real-time bank-to-bank system