Why Greek, Roman and Norse mythologies are overused, where others rarely get used?

Pretty much every place where humans lived on for any period of time has had a devastating flood event, so it's a "no brainer" when you think about it, much like how most (every?) ancient religions saw Sol and Luna as some sort of god/dess

I also think that it's interesting. And I wonder if it's something shared by the "collective memory" of humankind, or if it's just that flooding events are so common and impactful that any culture is almost certain to develop that myth, given enough time.

To be frank the only ones that I know a bit in depth are the Guaraní and Kaingang ones, as those are the two main Amerindian peoples here in Paraná. I'm completely clueless on the Yanomami one, for example.

For further kawaii, I think that the Mboi-Tatá is based on the same constrictor boas that some people keep as pets. It doesn't inject venom, it sees larger animals as potential prey, and it likes to sleep in burrows, just like the boa.

There's quite a few other Guaraní myths involving serpents, like the Mboi Tu'i, or "serpent-parrot". It's a giant serpent with two legs around the waist, the head of a parrot, and plumes on the head and the neck. It has cursed eyes and a terror-inspiring scream, but it eats only fruits and protects aquatic animals, specially amphibians.

In what I believe to be the Pre-Columbian version of the myth, that serpent-parrot was the second of the Seven Legendary Monsters - the offspring of a cursed couple; their father was the evil spirit Taú and their mother was the most beautiful woman of the tribe, Keraná, who sloped together.

In another story the Mboi Tu'i was actually born as a parrot, and it had free access to The Land of No Evil. However as some mestizos shared him fermented wasp honey (i.e. mead) and the parrot got drunk, it spilled the beans with the mestizos and told them how to enter The Land of No Evil. As a punishment the parrot was partially transformed into a snake, losing the ability to fly and reach the sacred land.

Accordingly to some Guaraní myths, Kuarahy (the Sun) and Jasy (the Moon) are brothers, with the Moon being the younger one. As their mother gave birth, the celestial jaguars (a type of evil spirit) killed her and stole the children, raising them in her place. The children eventually grew up and learned the truth, unleashing their vengeance towards the jaguars, killing almost all of them. They spared a pregnant female, who would eventually become the ancestor of all mundane jaguars.

That's the origin of such enmity between man and jaguar - as men took Kuarahy and Jasy's side, and the jaguar their ancestors'. (Jaguars fulfil in Guarani mythology a role similar to the bear in the European ones. It's an animal to fear, to revere, to avoid, to respect, but that you're still bound to fight).

In another myth, that would happen before the brothers' revenge, one of the celestial jaguars (called Charia) was fishing on a river. Charia didn't notice the brothers, so Kuarahy decided to troll Charia a wee bit - diving and pulling Charia's hook and line, to imitate a large fish. Charia pulled the fishing rod with all force, falling behind, amusing the brothers. Kuarahy did this three times, and in all three times Charia fell for it.

Then Jasy, amused, said: "now it's my turn!". He dives and pulls the hook, like his brother did. However this time Charia was quicker - he fished Jasy, killed him with a wooden club, and brought Jasy's corpse home as if it was fish, to eat with his wife.

As they were cooking "the fish", Kuarahy went to Charia's home, and he was invited to partake on the fish. He thanked Charia, but he said that he'd only eat some maize soup; he also asked for the fish bones, allegedly for stock. He took those bones to a remote place, and used his own divinity to resurrect his brother.

That's why lunar eclipses happen - the Moon gets devoured by the evil spirit, with the reddish hue in the sky being the Moon's blood. And the Moon only resurrects, always as a full Moon, because his brother Sun saves and resurrects him.