Well...South Africa's new constitution is similar to America's constitution, so I guess they liked how our constitution works and decided to make a constitution that's works well. It worked though! Their constitution lays the foundation for an open society based on democratic values, social justice, and fundamental human rights. Just like us!
They have a president. They have a government. They even have a judicial branch. Just look how successful they are now and look how they were back then. Then compare those two together to see the results.
This constitution contains a bill of rights, modeled on the chapter of fundamental rights in the interim constitution. It also ended the power sharing requirements that were basis for the government of national unity under the interim constitution.