What made the united states unique among the countries that had undergone similar democratic revolutions?

A) The hillsides, Inca farm used slash and burn farming methods.

Some of the tribes that used slash and burn method of farming were the Aztec, Inca, and Mayans. The method included cutting down trees and woody vegetation to clear the fields then followed by leaving the exposed vegetation called slash to dry out.  

Burning the area resulted in a soil rich with nutrients needed in crop planting to have a great harvest. However, after 3 years the soil loses the nutrients resulting in low crop production forcing farmers to look for different farming land. The abandoned land recovered after five to 20 years.