Some foods from native plants I have enjoyed over the years are:

Chokecherry, particularly chokecherry syrup
Wild currant which makes an excellent jelly
Camas root which has a small bulb that tastes rather like potatoes.
Bitterroot, an acquired taste in most cases.
Servias berry, bland but very plentiful and a staple unit in pemmican in the Pacific Northwest
Huckleberry which is certainly not the common blueberry. They are of a different genus.
Wild onions, either boiled fresh or dried.
Nettles
Wild strawberry
Wild cherry
Native watercress, which is somewhat different to the naturalized european varieties.

Try 'em sometime.