Greenbriar (Smilax spp.) is a common genus found all over the world. The one pictured above is Common greenbriar (Smilax rotundifolia). However, it appears that all smilax are edible, and not just that, but every part of them. Eat the starchy roots, eat the leaves, eat the shoots, and eat the berries. I spent some time looking up the toxicity and edibility of various native species and found nothing. Then I came across this post on wildflower.org: “The Botanical Dermatology Database lists the only possible injury from any Smilax species as being a mechanical injury from the thorns.”
Regarding Common greenbriar, it is a vine that uses tendrils to climb other plants, often becoming a tangled mess. Essentially, it is not a very attractive plant in the formal garden sense, but produces a lot of green and a lot of food. Smilax rotundifolia is also host to 13 different caterpillar species and the fruit is a valuable food source for other wildlife.
Note: I did find one source that said smilax can be flammable, so be careful.
Map Source:
USDA Plants Profile
Photo Credit
https://commons.wikimedia.org/w/index.php?curid=6856854