American Lotus is a great food source found in the southeast and a few places north of the Mason Dixon line. The roots, shoots, flowers and young seeds area all edible. The root however is the most important in a desperate survival situation because if you find lake or pond with this plant in it you will likely find numerous plants each with a root that can provide substantial mass of edible food.
The roots of a single American Lotus is resembles something like a banana or squash combo. The roots are best when harvested in the fall, so if you can designate American Lotus root as a fall food source. If you have any doubt about the id of the plant you can cut the root in half and it will look like a wagon wheel or the cereal honey combs. Basically a circle shape with a number of swiss cheese like holes running in a circular pattern.
American Lotus roots are sweet and can be eaten as raw, fried. Young lotus roots can be added to salads while the larger roots best used in soup type meals. Just like acorns the roots can be soaked in water to remove some of the bitterness but this is optional.
The new unopened leaves are edible like spinach. The stems can be peeled and then cooked.
American lotus puts up seed pods with about 20 seeds. The seed pods are very distinctive and look like a shower head.
The seeds although edible pretty much suck raw. The seeds can also be boiled and made into a paste and combine it with other foods to help it go down. The seeds of mature seed heads are worse and much more bitter. It is best to eat the seeds when they are young. Simply collect them boil them in water for 15-22 minutes then shell them and eat them like that. This way they aren't bad. Many people even like them. Older seeds can be ground in to flour, and best if used to extend other flours in my opinion.
The root, seeds, unopened leaves, and stems as mentioned are all edible but each will taste better if they are first soaked in water to help leach out some of the bitterness.