In the last few days there has been a few posts on the conlang-l list about conlangs based moribund or dead languages. Since Native American languages were named, it reminded me of thoughts that have rolled around in my head from time to time over the last year or so.
I don't really deal in auxlangs, but it a moment of musing it occured to me that the only real chance one has of being widely adopted in the U.S. is if Native Americans one day get sick of conducting their inter-tribal business in English and decide they need something else. No existing Native language would probably really work for several reasons. First, an auxlang should be a lot easier than a natural language to learn, and there not a single Native language easy enough to reasonably fill the auxlang role. Second, there would be political problems — there are standing tensions between some tribes, some of which go back very far indeed. For example, there are probably very few Hopi or Navajo who would be willing to learn each other's language (you can google their land dispute on your own).
I'm not actually going to concoct a North American Native auxlang, but I offer here some of my thinking about how one might go about such a thing, with a few hints of what this might look like were I to do so.
Easier — not Easy. Any NAN-auxlang would have to take into consideration the fact that large numbers of Native Americans are now monolingual English speakers, but I don't think a goal should be to make the language familiar to speakers of European languages. There are very widespread areal features in North American languages, and as much as possible these should be drawn on in creating the language. I would, for example, include regular conjugation of verbs, very probably by prefixing. I've been using WALS to verify commonalities in N.A. languages.
The Stock. Taking inspiration from Lojban, as a practical matter I'd draw on the largest language families — Na-Dene, Algonquian, Uto-Aztecan, Siouan and Iroquoian. The Salish family might belong in there, too, as well as Kiowa-Tanoan and Muskogean. For the many isolates, we'd have to rely on areal similarities.
Phonology. A simple, 4 or 5 vowel system. I would, sadly, omit tone, and, more happily, nasalization.
For the consonants I would at the very least include /p/ /t/ /ts/ /k/ /s/ /n/ /m/ (maybe only one nasal) /w/ /y/ /ʔ/ /h/ (which could be [h] or [x]) and /l/. I would probably include /ɬ/. That's less common the further east you go, but occurs even in the Muskogean family. I was prepared to omit ejectives at first, but now I think I'd consider including them. Thanks to Na'vi, I know that most L1 English speakers can learn them pretty easily, and they really extend pretty far east, too.
I'd keep syllable structure simple or at most moderately complex, allowing, say, syllable onsets to have /w/ or /y/ as a second element (if not, I'd add /kᵂ/ to the base inventory), maybe a nasal coda. Accent strictly initial or final.
Grammar. In favor of Esperanto's gender system, I'd differentiate by animacy. I'm still not sure if I'd include 4th person/obviation mechanics.
Rather than tense, the verb would be more preoccupied with aspect, by regular suffixing. A future tense adverb might sneak in.
Nominative-accusative alignment, but no case marking. Subjects of verbs would be person prefixes; not sure about objects, but I could be talked into putting those into the verb, too.
Plenty of North American languages have some sort of classifier system. I'm not sure that I'd add those, or if I did it'd be a very simple and regular system, attached to numbers only (i.e., I would regretfully lay aside the verbal encoding that goes on in so many languages).
At the very least, reportative evidential. Maybe inferential.
I probably would include adjectives as a word class, maybe with special marking for predicate adjectives.
Haven't decided on word order, probably SVO with SOV a strong contender.
Vocabulary would be churned through some automatic system to find any mnemonic cross-family similarities there might be, and ensure equal representation.