Thank you.
Unfortunately, USPS hands over the parcels to our government postal service (South African Post Office - SAPO). This service has all but collapsed and many, if not most, parcels just disappear - even if USPS priority or signed is used. I know this because packages I have ordered from the USA and other countries, which use their postal systems (even with tracking), have almost all never arrived or be found again due to this handover.
The only way now to guarantee any delivery to South Africa must be to use one of the private courier companies such as DHL, UPS, Aramex etc. Can you arrange a door-to-door using one of those?