(Maybe the wrong sub) What is the avergae or normal range for tribal cultures like the German tribes that clashed with Rome or the natives of the North American continent?

Your main question is nearly impossible to answer because "tribe" is perhaps the most commonly used useless word in modern anthropology. It's a consequence of anthropology, especially American anthropology, living in Elman Service's shadow. Service divided all human societies into one of four categories. From smallest to largest and from the most sociopolitically egalitarian to the least (generally speaking), they are bands, tribes, chiefdoms, and states. "States" include everything from ancient city-states in Mesopotamia to massive modern nations like Russia, Canada, the United States, and China. There are other traits associated with each category, but I'll set a full discussion of Service's system aside for now. Long story short, it's handy for theory and an absolute mess in practice. All sorts of things get labeled as tribes while having only the vaguest similarities. About a year ago, we had a feature topic about the use of the word "tribe", that you might be interested in.

To give you an example in practice, consider the Miami (Myaamiaki in their own language, -aki being the plural). When first encountered by Europeans in the later half of the 1600s, they were living in the area around modern day Chicago westward to the Mississippi and north to the Wisconsin River, with their largest town in the northern end of this area. This wasn't their pre-Columbian homeland, however. Until recently, they had actually lived on the other side of the lake in southwestern Michigan and northeastern Indiana but the Beaver Wars that had begun in 1649 and pushed them west. At this time, the Miami were composed of six subgroups: the Atchatchakangouen, the Wea, the Piankashaw, the Kilatika, the Pepicokia, and the Mengakonkia. When the Beaver Wars came to an end in 1701, the Miami first moved back to their earlier homeland but soon found the Wabash River valley more to their liking and settled along its entire lengthy, establishing Kekionga, their principal village / capital the headwaters of the river (modern day Fort Wayne, Indiana). The southern two-thirds of Indiana, western Ohio as far Great Miami River, and parts of southeastern Illinois were Miami country through the 18th Century. Kind of.

By the time the Miami moved back to Indiana, the Kilatika, the Pepicokia, and the Mengakonkia had been entirely absorbed by the other three. Soon after settling the Wabash Valley, the Wea and Piankashaw declared their independence from the Miami, leaving the Atchatchakangouen as the last Miami group. Today, the Wea and Piankashaw no longer exist and their modern descendants are (in part) citizens of the Peoria nation, which had been one of the constituents of the closely related Illinois Confederation (The Miami and the Illinois spoke the same language). So really, the Miami (ie, the Atchatchakangouen) controlled only the upper third of the Wabash in Indiana and some parts of Ohio, while the middle and lower Wabash were Wea and Piankashaw respectively.

So, in 1701, were the Miami a tribe? Were they confederacy of tribes? Early French reports don't talk about the Miami's political system like they do more definitive confederacies, but instead talk about a singular "great chief of the Miamis." - in 1671, this was a man by the name of Tetinchoua. Were the Miami perhaps actually a chiefdom? There's some evidence for this archaeologically, but only scant evidence historically (that's one of the problems with the "chiefdom" classification - it almost always evaporates under scrutiny, resolving into their tribes or states). Maybe Tetinchoua was a military commander who had been granted emergency powers during the Beavers Wars, since the Miami seem to lose any "chiefdom" traits after the Great Peace of 1701. While Service would disagree, the word tribe has been used to describe an ethnic group, regardless of political organization (this is the definition that drives the Africanists among us crazy, and rightly so, since it's loaded with all sorts of baggage) - but applying that definition to the Miami would also lump them in with the Illinois. They speak the same language and when Little Turtle, the most prominent of the Miami leaders in the late 1700s, described the land claimed by the Miami forefathers, he described all the lands then settled by the Miami, the Wea, the Piankashaw, and the Illinois Confederacy (this map basically covers the same area he described).

Depending on how you define "tribe" and when you happen to be looking, that would greatly affect the size of Miami country.

was the Iraqois confederacy a single cultural group or were the member tribes fairly distinct?

A bit of both. They're a single political unit, much like the modern United States, but cultural distinctions between the nations that are more significant than the differences between US states. But give us another 400 years, maybe the US will get there too.

For most of its history, the Haudenosaunee (the Iroquois Confederacy) consisted of five nations (or tribes if you prefer). These are (from east to west) the Mohawk, the Oneida, the Onondaga, the Cayuga, and the Seneca. The Tuscarora are called the Sixth Nation, and while they admitted into the confederacy in 1722, they couldn't full participate in the confederacy politics until after the Revolutionary War. The non-Iroquoian Lenape and Shawnee had similar status while under the protection of the Haudenosaunee prior to the French-and-Indian War, which explains the occasional reference to the "Seven Nations" in the Ohio Valley (there's also a Seven Nations of Canada at this time, but that's a tangentially related confederacy on the St. Lawrence). We'll set the non-Iroquian nations aside for now. As for the Six Nations, each speaks its own language, which are all part of the Iroquoian language family. Seneca and Cayuga are pretty closely related, with Onondaga being a bit more distantly related. Mohawk and Oneida pair up as close relatives too. Tuscarora is the most distantly related, which makes sense considering that they were living in North Carolina before 1722. More surprising, however, is the fact that Tuscarora is not more closely related to Cherokee, their most significant Iroquoian neighbor in the south. To help illustrate the differences, here's how you count to five in each language:

Language	One	Two	Three	Four	Five
Seneca	ska:t	tekhni:	sęh	ke:ih	wis
Cayuga	ska:t	tekhni:	ahsęh	ké:ih	Wis
Onondaga	ská:ta	tékni	áhsę	kayé:i	hwiks
Oneida	óskah	tékni	áhsę	kayé	wisk
Mohawk	éskah	tékeni	áhsę	kayé:ri	wisk
Tuscarora	ətsi	né:kti:	áhsə	həʔtahk	wisk
Cherokee	sokwuhi	thaʔli	tsoʔi	nəhki	wisk

The Six Nations also all have matrilineal clans, but the specifics vary. They all have at least one Bear, Turtle, and Wolf Clan. For the Mohawk and the Oneida, that's it. The Onondaga have two Wolf Clans, as well as a Turtle, Beaver, Ball, Deer, Eel, Bear, and Hawk Clans. The Cayuga have Turtle, Bear, Deer, Wolf, Heron, and Snipe Clans. The Seneca have Turtle, Bear, Wolf, Beaver, Ball, Deer, Heron, Snipe, and Hawk Clans. The Tuscarora have Great Turtle, Small Turtle, Wolf, Bear, Beaver, Snipe, Ell, and Deer Clans (the Wolf and Bear clans may have also been subdivided like the Turtle Clans, but the historical record isn't clear on that matter, and several Tuscarora clans have died out completely now.

Also, if you attended an old fashion Grand Council meeting, you'd be able to tell which nation each delegate belonged to just by looking at them. Each nation had its own unique style of headdress for such formal occasions.

Each nation also had some unique ceremonies. The Gayanashagowa - the oral constitution of the confederacy - protected these, saying "The rites and festivals of each nation shall remain undisturbed... ." If you follow the link and jumped down to the "Religious Ceremonies Protected" section, you'll see the quote, as well as references to a few confederacy-wide "national holidays" established by the constitution, with the Midwinter Thanksgiving being the most important.