Prologue: Dozens of televisions announce random bits of news, gossip and commercials. Everyone is fixated on his or her own television. Fed up with the state of the union, the company explodes in anger ("American Idiot").

We find ourselves in a suburban wasteland at some point in the recent past. We meet Johnny. He's almost 30 and he's done nothing with his life. He goes to commiserate with his friend, Will ("Jesus of Suburbia"). Their friend, Tunny, shows up, and they party. When the three of them run out of beer, they head to the 7-11, where Tunny exposes the do-nothing, go-nowhere quicksand of their lives ("City of the Damned"). They get riled up, and Johnny challenges his friends to care ("I Don't Care"). Heather appears. She is pregnant, and doesn't know what to do ("Dearly Beloved"). Meanwhile, a decision is made. Johnny, Will and Tunny will head to The City to start a new life. At the last moment, Heather reveals to Will that she is pregnant with his child, and Will decides to stay home ("Tales from Another Broken Home").

Johnny and Tunny take a bus across the country. As expected, the America they find sickens them, and they redouble their commitment to forging their own path ("Holiday"). They arrive in The City and share a cheap room at a dive hotel. Days pass. Tunny sleeps, but Johnny walks out into the night to claim his connection to the city. He even sees a lonely girl in a window and flirts with her ("Boulevard of Broken Dreams"). Back in the hotel, Tunny wakes up. Disillusioned with The City, he has a television-induced mystical revelation ("Favorite Son"). Mesmerizing images of power and patriotism inspire Tunny to enlist in the military ("Are We the Waiting"). Johnny returns to the hotel to find Tunny gone. Alone and desperate, Johnny conjures an all-powerful alter ego, St. Jimmy. Surrounded by disciples and jacked up on St. Jimmy's charisma and drugs, Johnny tracks down the girl in the window, Whatsername, and makes his move ("St. Jimmy").

Johnny hooks up with Whatsername. Back in suburbia, Will and Heather struggle to keep their relationship alive, but Will's inertia threatens to get the best of him. Meanwhile, in the Middle East, we find Tunny in combat, where he is injured ("Give Me Novocaine"). Johnny is smitten with Whatsername and wants to celebrate, but St. Jimmy has other plans for them ("Last of the American Girls/She's a Rebel"). St. Jimmy gives Johnny and Whatsername some high-grade heroin, and they shoot up. By this time, Will and Heather's baby has been born, and Will is increasingly oblivious as Heather tenderly commits herself to her baby's future ("Last Night on Earth"). Heather has had enough of Will's pot-and-alcohol-fueled apathy. Despite Will's protestations, she takes the baby and walks out ("Too Much Too Soon").

Tunny is in a military hospital in the Middle East with three other injured soldiers ("Before the Lobotomy"). His left leg has been severely wounded. In a morphine-induced hallucination, a mysterious burqa-clad seductress appears to him from the sky. She pulls him into an ecstatic mid-air dance ("Extraordinary Girl"). The mirage disappears, and he is left with his fellow soldiers in agony ("Before the Lobotomy – Reprise"). In The City, Johnny sings Whatsername a beautiful love song that he has written for her ("When It's Time"). This propels St. Jimmy to action. Threatened by Johnny and Whatsername's intensifying connection, he retaliates by trying to separate them. Johnny's need for drugs suddenly increases. As he ties off and shoots up, he pictures Will, and they reiterate their old credo ("Know Your Enemy").

Three simultaneous events: In the military hospital, Tunny's leg has been amputated. His nurse, the Extraordinary Girl from his fantasy, gives him a sponge bath and comforts him. Back in suburbia, Will is alone, and Heather is somewhere far away, with their child. In The City, Whatsername appeals to Johnny to clean up and get serious about his life and their relationship ("21 Guns"). Johnny can't handle it and taunts her under the continuing influence of St. Jimmy. Whatsername has had it and she leaves Johnny ("Letterbomb"). Johnny hits rock bottom. He longs for better days ahead, Tunny longs for home, and Will longs for all the things he's lost ("Wake Me up When September Ends").

Johnny commits to getting clean. St. Jimmy relaizes that his days are numbered, and the Johnny/St. Jimmy matrix explodes in the metaphorical suicide of St. Jimmy ("The Death of St, Jimmy"). Johnny joins the work force. He doesn't like it too much ("East 12th St."). Will, out of grass and all alone with his television, bemoans his outcast state ("Nobody Like You"). He finally gets up off the couch when, suddenly, Heather appears on television with her new rockstar boyfriend ("Rock and Roll Girlfriend"). Will freaks. He heads to the 7-11, waiting for something to happen. Johnny returns home, as does Tunny. The three friends reunite in the parking lot of the 7-11. Tunny introduces his Extraordinary Girl, who has returned home with him. Heather and her rock and roll boyfriend arrive. In an uneasy truce, she allows Will to show his kid to his two best friends. Other friends show up, too, to greet the three guys, whom they haven't seen in a year ("We're Coming Home").

Epilogue: A year has gone by. Johnny reflects on the mistakes of his past and, for the first time, he can live inside the struggle between rage and love that has defined his life. With this acceptance comes the possibility of hope ("Whatsername").