William Blake's America: a Prophecy is a mythologized version of the founding of America as a country. Blake creatively—and vividly, as the original work featured eighteen illustrations of its mythological subjects—portrays a battle between the rebellious America and the domineering Britain. The story is an allegory for the triumph of creativity and novelty over reason and tradition.

Blake's America should be viewed in its context as first of a series of three poems. The next was the similarly structured "Europe: a Prophecy" (which describes the foundation of Europe followed by its infestation by war, rebellion, and sin) and and the last was "The Book of Los" (which recounts the fall of Blake's mythical zoa—an incarnation of primordial man—Urthona into the degenerate human form, Los). Los is depicted as a smithy god who works with a hammer, and he is the father of Orc (who appears in "America, a Prophecy"). Los thus represents creativity, and Orc represents restlessness in the form of fiery rebellion (Blake's mythology is very similar to other religious pantheons in the sense that deities are personifications of abstract forces and emotions).

"America: a Prophecy," like the other works in Blake's continental prophecies, are is heavily politicized. It tells the story of the American Revolution by adducing historical figures such as George Washington and Benjamin Franklin, but also mythological beings such as Orc (a fiery spirit of rebellion) and his counterpart Urizen (a deity who appears as a leprous old man representing reason and law).

The Angel of Albion (a personification of England) tries to summon his Thirteen Angels with his trumpet, but these angels abandon Albion in favor of America. The Angel of Boston in particular rouses his cohort against obeying their former master, Albion. Left without his Thirteen Angels (who represent the colonies), Albion sends a plague to America, which Orc repels with fire and sends back to England. As a result, all of England (Bristol, York, and London) is overtaken by sickness. Urizen (the spirit of reason) emerges from his shrine as an old man, crying in pity for his beloved Europe (and Urizen can be interpreted more broadly as the spirit of the Enlightenment).

By showing Orc victorious and Urizen, the Thirteen Angels, and Albion thus defeated, Blake suggests the triumph of rebellion and creativity over law and reason.