One of the things you should remember is that ALL food that we grow now came from wild species. If you have a garden, it will be easier for you to pick out things that look familiar. If you do not grow your own food, you can still find things to eat in the wilderness that will not be too odd.
Apples in bloom and in fruit.
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Fruits are some of the easiest to find and recognize. Apples, the import that took over America, can be found growing wild in most parts of the country, except for the really arid areas, and even then, there may be verities available. One thing to keep in mind is that the wild apples are grown from seed, not grafted, so the apples you find are going to be smaller, and possibly quite tart. Things that look like apples include crab apples and wild pears.
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Other fruits that are easily recognized are berries of all types. One word of caution, Red berries should be avoided. Honeysuckle is a great perfume, and the flowers can be sucked of their nectar, but the berries are quite acidic and are bad in large quantities. What you should look for in North America from the middle of June on are things like raspberries, blackberries and mulberries. Raspberries and blackberries are on 'canes' that can create thickets in sunny areas. This means that the juiciest berries are not where human hands can get to them normally. A large knife, like a machete, can change that. Mulberries are tree or bush fruit, which means that they are more likely to be at the edge of a clearing, and up. There are male and female mulberries, so if you see a tree without fruit beside one that does, do not be worried. With all fruits, inspect them and wash them. If possible, cook them or rinse in hot water before eating when in the wild.
If you are in an area that has farms, it is possible that some of the seed blew into gullies, ditches and such, so around the middle of July, possibly sooner, look for stray corn stalks, wheat and other farm strays.
If you are having problems finding fruits and vegitables in the wild, CCD could be the problem.