I like this thread. Despite the indications and rumors that Germany/Nazis sent anthropologists into the US to comb for written native American languages just in case the US used such codes, the rationale why the US probably did not embrace native American "code talkers" more is questionable. Check me if I'm wrong: but didn't the Cherokee Nation have the only written language? The other half of the problem would be to have either a Japanese or German translator adept in the spoken language: not going to happen, certainly not tactically. They lost a resource. Also, not using American Indians in our reconnaissance and special operations units was again naïve or ignorant. We have supreme examples such as the Alaskan Eskimo Scouts, Castner's Cutthroats, and the southern US Cavalry...the US Cavalry units at the time were mostly populated by "colored" troops, so they were broken up, but some of the US Scouts were still in the Army until 1947. Albeit Ft Huachuca was a legacy for them and once it close in 1947 that was it, closing almost two centuries of American Indian Scouts. The active duty Scouts were relegated to mule skinners and fence tenders.
If you want to read more into the Navajo code talkers, then I highly recommend Chester Nez's memoirs Code Talker. Chester was the last of the original Navajo code talkers alive, unfortunately he passed away earlier this year.