The statement that best explains the difference between the Mayan civilization and the Roman Republic is:
"The Mayan civilization was led by a demigod monarch, and each Mayan city operated independently with its own culture and laws. The Roman Republic was a centralized system led by two consuls and a senate."
This statement correctly highlights the structure of leadership and governance in both civilizations, emphasizing the decentralized nature of the Mayan city-states compared to the more unified political system of the Roman Republic.