I wonder which ethnic cuisines would be unsustainable for a restaurant. Like, say, Amerindian cuisine. Acorn and corn?
From what I hear, the Western states have quite a few Native American-run take-out places that specialize in fry bread and Indian tacos. Here's an example of one that has a menu:
http://www.auntiesfrybread.com/menu/
This is a fascinating idea and very creative, but what would the actual dishes and food items be? :/
This thread is making me hungry. Let's talk actual cuisine.
The Mitsitam Cafe in Washington DC's National Museum of the American Indian might offer a few ideas:
http://www.nmai.si.edu/subpage.cfm?subpage=visitor&second=dc&third=mitsitam
Iroquois leaf bread is very similar to tamales, so that could work as a fast food item.... Or perhaps come other type of Native American cornbread, like hoecakes and johnny cakes.