Mexico’s coat of arms depicts an Aztec legend; one saying the gods told them to build a city where they find an eagle on a nopal (prickly pear cactus) eating a serpent; hence came Tenochtitlan (now Mexico City). The other image on the right comes from the other side of the world and dates back farther in time (it is a 6th century mosaic flooring from the Grand Imperial Palace in Constantinople). Coincidence? Transcontinental travel? Jungian synchronicity?
I’m guessing that early man had a snake problem and any enemy of the poisonous snake is a friend of man. King-snakes which killed other snakes made the good list along with other snake killers like cats and birds.