Only a few references for the west? Try "Western Edible Wild Plants" by H D Harrington. It is probably out of print, being published in 1972, but I am sure there are hordes of later publications. Try looking under "Ethnobotany." You really only need to know one word for western edibles - pinyon. They are not only fairly abundant, in a good year, but tasty as well. And then there is yucca, prickly pear, mesquite, and cattail. These are mentioned in lots of references.

Actually the high desert mountain areas have fewer plant sources than the surrounding lowlands, esp the pinyon-juniper belt, but at higher elevations, you can encounter wild strawberries, tasty, if not useful for long term sustenance.