The denotation of these various peoples as tribes is academically problematic to begin with. The word tribe as used in colloquial English is rather ambiguous in its definition as compared to its use in the scientific field that concerns itself with its study: anthropology. In the field of anthropology the term is used to describe a small-scale community that (as of yet) lacks the economic development to support a domination by an elite and as such is egalitarian in nature (edit: commentators more at home in anthropology have interjected the fact that this definition (A) contains elements attributed to the definition of bands instead, and (B) is out-of-fashion, especially in the United States), whereas its definition in colloquial use seems to range from this strict description on one end to any people or (proto) nation that cannot be strictly defined as a country or kingdom on the other end; often as a placeholder in lieu of a better denotation. This gives rise to the myriad of "tribes" in literature and media that somehow have fundamentally different anthropological structures. So to answer the first part of your inquiry: it is inaccurate and (academically) unsound to denote all these peoples as tribes.

Considering the specifics in context to the peoples you mentioned as examples: as we can now deduce from the stark difference in the colloquial and academic use of the word, these peoples were vastly different. I miss the expertise required to confidently attribute the Native American peoples that were part of the Iroquois the correct anthropological marker - if their economic development remained relatively similar to those of pure hunter-gatherer communities, they could possibly indeed be classed as tribes in the academic fashion - but for the inhabitants of Gaul, at least during Roman times (an important caveat), it would be more correct to use the term chiefdoms: a more complex society with enough economic development to form a small local elite, in the context of "barbarian" Europe the Gefolgschaften (roughly warrior aristocracy) based on the development of a gift-exchange system, where warlords are able to project their power by utilizing an armed following in exchange for prestige goods obtained through warfare, such as weapons and horses. Apart from the obvious cultural differences it is likely that Native American and European sociological structures would have been far more similar when the latter was largely also still devoid of agrarian development and instead mainly dependent on hunting-gathering for sustenance (agrarian surplus is one of the main ways in which a primitive economy is developed), hence the caveat of Gaul in Roman times.

In short, the process to compare these supposed "tribes" is to first see whether they meet the parameters of being defined as such in an anthropological sense. Hope this helped a bit!

This is something I have talked about quite a bit with respect to African societies. We had a Monday Methods thread a few years ago where contributors gave answers for how their specific fields define the word "tribe" and whether they use it or avoid it.

I also did an episode of the Askhistorians podcast where I talked at length about why "tribes" were in many was a colonial invention in Africa. In that thread I also provide several recommendations for literature about "tribes" and ethnicity in Africa.

Of the recommendations, I'd really, strongly recommend trying to find a copy of The Notion of Tribe by Morton Freid. His book takes a global comparative perspective, examining examples of "tribal peoples" from Africa, North and South America, the Pacific islands and Asia to assess if the term "tribe" is a meaningful term.

For specifically African context, I'd recommend Carola Lenz's article " 'tribalism' and ethnicity in Africa: a review of four decades of Anglophone research" as a strong overview of the literature up to the mid-1990s.