In January 1776, shortly after the signatories finalized the Declaration of Independence, a treacherous act unfolds as Benedict Arnold ((played by Andy Samberg)) betrays his fellow patriots, leading them to their deaths at the hands of the British. His plot thickens as he confronts a dramatic moment at Ford's Theater, where George Washington (portrayed by Channing Tatum) and his lifelong friend, Abraham "Abe" Lincoln ((Will Forte)), are watching a play. A disgruntled Abe argues about the exorbitant prices at the theater, lamenting how "a mere $5 item is inflated with $30 in taxes."
In a shocking transformation, Arnold morphs into a werewolf, violently tearing apart the signed declaration and fatally attacking Lincoln. Just before his demise, Lincoln urges Washington to end the American Revolutionary War and to honor the nation as "America." The cunning Arnold spares Washington, dismissing him as a party boy who lacks the serious demeanor of a leader. However, undeterred, Washington retaliates wielding chainsaws against Arnold's barbarism but finds himself thwarted when Arnold escapes via a transport provided by Zebbie Gillese.
At Lincoln’s funeral, where the somber atmosphere contrasts sharply, Washington, who claims the distinction of inventing peanut butter, encounters Martha Dandridge ((Judy Greer)). Their intimate encounter inspires Martha to encourage him to press forward with the revolution. Joining forces with the party-loving Samuel "Uncle Sam" Adams ((Jason Mantzoukas)), a troublemaker in Martha's adult kickball league, they assemble a motley crew. This includes the brilliant scientist Thomas Edison ((Olivia Munn)), who must defend her life and theories from the British while denouncing any sorcery accusations. Additionally, they find support in the form of Native American hunter Geronimo ((Raoul Trujillo)), the skilled tracker wary of Washington's motives, and aspiring equestrian champion Paul Revere ((Bobby Moynihan)).
Their quest leads them to confront Arnold at a lively bar in Vietnam, where they cleverly deduce that their earlier escapades were not in vain despite their setbacks. In a tense encounter, Arnold bites Geronimo, forcing him to sever his arm to prevent transformation. As they pursue Arnold on Clyde, Revere's horse, the villain escapes on a Jet Ski through the Boston River, leaving Washington disheartened and contemplating surrender until Martha's loving encouragement reignites his spirit.
Their mission takes a daring turn as they recruit master blacksmith John Henry ((Killer Mike)) to forge a silver bullet capable of taking down Arnold. Desperate for the necessary resources, they embark on a heist to acquire a cache of silver spoons aboard the famed Titanic. Amid their adventure, they stumble upon the British’s insidious plans to manipulate individuals into betraying their own with a sinister tea-bathing ritual, but their mission is upended when the ship meets its watery fate, leaving them to concoct a cover story claiming the Titanic collided with an iceberg.
As events spiral, Arnold seizes Martha, who has caught the eye of King James ((Simon Pegg)), plotting a war machine alongside Arnold designed to obliterate the rebellion. Washington uncovers their clandestine meetings and sets a trap at Gettysburg, but the situation becomes dire when Clyde sacrifices himself to thwart Arnold’s explosive plans.
The climactic battle dawns, with Washington's hastily formed army facing off against an otherworldly British force led by a holographic King James, transforming the battlefield into a chaotic confrontation filled with fantastical elements. As Arnold evolves into a Mega Wolf, the tides shift when Edison ingeniously repurposes British weaponry transforming tea rain into a deluge of beer, resulting in an identity crisis for the British ranks revitalized as Americans, thus shattering Arnold's grip on power.
Months later, on July 4, 1776, Washington commemorates the inception of America with a grand ceremony at his monument. However, as the spirit of Abe returns to present him with a mended Declaration, the festivities devolve into chaos when the crowd ignites a heated debate over pressing issues such as racism, women's rights, and LGBTQ rights. Washington grapples with the overwhelming prospect of leading a nation rife with discord, foreshadowing the complex journey ahead for his country.
