https://babel.hathitrust.org/cgi/pt?...=344&skin=2021 (if you know any similar resource, please tell me)
Here are some of the largest tribes (based on high-end estimates for these tribes, close to the peak of their population):
Sioux - 150,000 in the year 1762 (estimate by James Gorrell)
Choctaw - 125,000 in the year 1718 (estimate by Le Page du Pratz)
Illinois - 100,000 in the year 1658 (estimate by Jean de Quen)
Shoshoni - 80,000 in the year 1822 (estimate by Jeddediah Morse)
Iroquois - 70,000 in the year 1690 (estimate by A. L. Lahontan)
Blackfeet - 60,000 in the year 1841 (estimate by George Catlin)
Apache - 60,000 in the year 1700 (estimate by J. de Urrutia)
Creek - 50,000 in the year 1794 (estimate by R. Brooke Roberts)
Hopi Pueblo - 50,000 in the year 1584 (Antonio de Espejo, Col. Doc. Ined.)
Huron - 40,000 in the year 1632 (estimate by G. Th. Sagard)
Tano/Maguas Pueblo - 40,000 in 1584 (Antonio de Espejo, Col. Doc. Ined.)
Comanche - 40,000 in the year 1832 (estimate by George Catlin)
Chippewa - 35,000 in the year 1650 (estimate by J. Mooney 1928)
Cherokee - 30,000 in the year 1730 (estimate by J. Adair)
Tuscarora - 30,000 in the year 1600 (estimate by D. Cusick)
Mohicans - 30,000 in the year 1600 (estimate by J. A. Maurault)
Navajo - 30,000 in the year 1626 (estimate by A. Benevides)
Jemes Pueblo - 30,000 in the year 1584 (Antonio de Espejo, Col. Doc. Ined.)
Pawnee - 25,000 in the year 1719 (estimate by J. B. Dunbar)
Neutrals - 20,000 in the year 1616 (estimate by S. Champlain)
Zuni Pueblo - 20,000 in the year 1583 (Antonio de Espejo, Col. Doc. Ined.)
Tewa/Ubates Pueblo - 20,000 in the year 1583 (A. de Espejo, Col. Doc. Ined.)
Cree - 15,000 in the year 1764 (estimate by J. Mooney 1928)
Delaware - 15,000 in the year 1600 (estimate by Th. Donaldson)
Pennacook - 15,000 in the year 1674 (estimate by D. Gookin)
Keres Pueblo - 15,000 in the year 1583 (Antonio de Espejo, Col. Doc. Ined.)
Abnaki - 15,000 in the year 1600 (estimate by J. A. Maurault)
Powhatan - 10,500 in the year 1612 (based on W. Strachey and J. Smith)
Tompiros Pueblo - 10,000 in the year 1630 (estimate by Alonso de Benavides)
I wonder if it even makes sense to count the population sizes of every tribe mentioned by Krzywicki, and then sum it up?
One of reasons why I doubt if it makes sense, is because some tribes could be descended from remnants of others, etc.
It is possible that not all of them existed at the same time.