i’ve never known any historian cite any date later than 1190 for the great law of peace

You mention Donald Grinde later in this comment, who notes later dates than 1190, as late as the 17th century.

i won’t get into the debates about whether or not the Haudenosaunee Confederacy influenced the eurocentric ideals of the US founding fathers. scholarship is very split on the notion with Donald Grinde arguing it was the most influencial framing system on the constitutional congress, Jack Rakove arguing against all influence, and Charles Mann arguing for predominantly european influence with some indigenous influence (this is where i view things since the colonists, Iroquois, Cherokee, Creek, and Chocktaw were frequently engaged in complicated systems of alliances). all this to say you find scholarship arguing against all influence the most compelling and i accept that this is a serious good faith position to take.

It's a popular position amongst some, but I find it extremely dubious for multiple reasons. I think that in large part it's an attempt to make the Iroquois Confederacy's government structure part of the legacy of the US government. But that misses the point that the Iroquois Confederacy's government structure is valid on its own accomplishments, without needing to be tacked on to the later Anglo government to be noteworthy and impressive.