I am very familiar with plants, more so in certain areas.

There are many plants that you can find across the nation. Look especially into introduced species (aka weeds).

Some of the more common and widespread edible species include: dandelion, burdock, thistle, purslane, plantain, cattail, pine, oak, grasses (watch out for ergo!), chicory, shepherd's purse, nettles, roses, mallows, and watercress (boil if eating submerged parts to kill water-nasties). I'm sure some of these have already been mentioned. Fiddleheads and horsetails are known to be toxic in quantity.

Be aware that many introduced plants are most commonly found on disturbed sites, and might have pesticide sprays or exhaust grime on them. Wash them.
Also, a few common edible plants are nitrate and/or selenium accumulators. Research this.
Learn the poisonous plants before you learn the edible ones, many edibles have poisonous look-alikes, and remember that with some plants and more often fungi, even a small amount can kill, so never experiment with them. "There are no old and bold mycologists."

I like it, Blast!