Neomysis americana is an "extremely common" species of opossum shrimp along the Atlantic coast of North and South America. The species has a disjunct distribution, being present in an area extending from the Saint Lawrence River to Florida, and separately in parts of Argentina (Blanca Bay, Anegada Bay and Samborombón Bay). N. americana is an important prey item for a number of fish species, including the Atlantic silverside, the bluefish and the windowpane flounder, Scophthalmus aquosus. Adults typically have a carapace length of .