Final answer:
The Andes Mountains in South America would make it difficult for cultural diffusion.
Step-by-step explanation:
The landform in South America that would make it difficult for cultural diffusion is the Andes Mountains.
The Andes Mountains are the longest mountain chain on Earth, stretching along the entire western region of the continent. They act as a physical barrier, restricting movement and making communication between different regions challenging.
This geographical feature hinders the spread of ideas, customs, and technologies, limiting the exchange of culture across South America.