The breakdown of chiefdoms eventually led to the development of

It led to the development of Native American societies.

Groups of Native Americans banded together to form Native American societies such as the Cherokee and Creek societies. So the answer is Native American Societies.

productive most commonly means: achieving or producing a significant amount or result.

explanation:

productive can also mean:

these depend on how the word productive is used. most likely productive will mean   achieving or producing a significant amount or result.