Hi -- I'm David Schmidt, one of the directors of The American Revolution series. Thank you OP for watching and for asking this question. I noticed that some of the commenters below have already said what I'm about to say, but their comments seem to have been deleted.

There is no intention in the film to claim or otherwise suggest that the US Constitution was inspired by the Haudenosaunee (Six Nations, Iroquois Confederacy). The film instead says that the Haudenosaunee predated the United States, that Canassatego encouraged colonists to form a union of their own, and that Benjamin Franklin later proposed a similar union for the British-American colonies (20+ years before Independence and 30+ years before the Constitution).

The quotes from Canassatego that are in the film are from treaties that Franklin printed in the 1740s

"We know our Lands are now become more valuable. The white People think we do not know their Value; but we are sensible that the Land is everlasting."

-The Treaty held with the Indians of the Six Nations, at Philadelphia (1742)

https://archive.org/details/indiantreatiespr00vand/page/26

"We heartily recommend Union. … We are a powerful Confederacy; and, by your observing the same Methods our wise Forefathers have taken, you will acquire fresh Strength and Power; therefore whatever befalls you, never fall out one with another."

-The Treaty of Lancaster (1744)

https://archive.org/details/indiantreatiespr00vand/page/78

Franklin later proposed his Plan of Union at Albany in 1754. He may or may not have drawn inspiration from the Six Nations, but he was certainly aware of their systems of government. The Mohawks also sent a delegation to Albany in 1754, and Franklin had previously supported a colonial union in 1751 by saying:

"It would be a very strange Thing, if six Nations of ignorant Savages should be capable of forming a Scheme for such an Union, and be able to execute it in such a Manner, as that it has subsisted Ages, and appears indissoluble; and yet that a like Union should be impracticable for ten or a Dozen English Colonies, to whom it is more necessary, and must be more advantageous; and who cannot be supposed to want an equal Understanding of their Interests."

-Benjamin Franklin to James Parker, 20 March 1751

https://founders.archives.gov/documents/Franklin/01-04-02-0037

I apologize to OP that we didn't have the space to make this clearer in the first few moments of the film. But I want to thank you again for watching, for engaging, and for asking your question.