Many cultural and evolutionary similarities are shared between the Far East/Oceania and the Americas, which led me to believe they were originally connected in the age of Pangaea. Many forget that Earth is a continuous sphere, which leads to confusion regarding the origin of many things.
Take Oceania and South America as an example. Many animals and biomes are similar: koalas and sloths, Haast eagles and harpy eagles, fruit bats, burrowing creatures, deserts, savannas, mountains, rainforests, high temperatures, areas of drought and humidity... the list goes on.
The cultures of the Far East and of the Americas are connected in their roots and origins, since the land was originally connected as well. This can explain similarities between myths like the ones you mentioned.