The answer is: different nations.
At the beginning o Franklin’s essay you can find these lines: “Savages we call them, because their manners differ from ours, which we think the perfection of civility; they think the same of theirs. Perhaps, if we could examine the manners of different nations with impartiality, we should find no people so rude, as to be without any rules of politeness; nor any so polite, as not to have some remains of rudeness.” Where he refers to the diversity among the Native American tribes respectfully using the term “different nations.”