In the Southeastern U.S., look for
kudzu (shouldn't have to look far) - the entire plant is edible - from roots to leaves.
Also in the Southeast:
pawpaws are a great wild food. They grow on trees, and they taste a little like bananas. There are recipes you can find online to make use of these fruits. I have made "banana bread" and muffins out of them.
One more in the Southeast - young
poke greens - these are really wonderful. They taste very similar to asparagus or Chinese broccoli. Just make sure you pick them young.
In the southern U.S. from Mississippi to Southern California, there is a squash vine called
Chayote, that grows rampantly. If you find (or plant) a patch of Chayote, you'll have an excellent food source for several months a year. The squashes are very, very ugly, but taste great. You can cook them just like baked potatoes, or use them to make zucchini bread.