"Back in the day," some say, and the rest of the sentence is sure to be some ode to the good old years. "Wait until tomorrow," others advise, and the rest of the sentence is likely to be a surmise about how great the future will be.
But history is not a straight line. Societies rise and decline, but often not in constant movement. Think of a roller coaster that doesn't loop but actually goes somewhere: At any particular moment the movement may be upward or downward, but the cars always move forward.
Some say the film equivalent of the Great American Novel is The Godfather, but that trilogy depicts America as a tragedy. The Rocky series—leaving out the execrable Rocky V—is a better representation of the American Dream. But if you're looking for the American Nightmare, try Death Wish III (1985), the second sequel to the famous Death Wish (1974) starring Charles Bronson as Paul Kersey, a man who takes vigilante action following the murder of his wife and rape of his daughter by feral muggers.
In Death Wish III, Kersey returns to a New York City (Death Wish II has him cleaning up part of Los Angeles) filled with uncivil war. A .38 revolver is child's play: Kersey's adversaries form a wild army, and against them his weapons of choice include a Wildey .475 caliber handgun, a Browning air-cooled machine gun, and a L.A.W. (light anti-tank weapon) handheld rocket launcher. Many decent folks are killed but the body count is especially high among the hoodlums, dispatched to the cheers of previously cowed residents watching from their apartment windows.
I'm not recommending Death Wish III except as an over-the-top study of what could have happened to America's cities—but veteran journalist Pete Hamill notes in Downtown (Little Brown, 2004) that "by the 1970s menace was becoming more general." Here's his description of New York City: "Children of ten and eleven formed packs, attacking the shoppers from Macy's and Gimbel's like schools of piranha fish. The newspapers called them 'feral youths.'. . . Toward the end of the 1970s, every New Yorker, male and female, white, black, and Latino, had learned to live with fear. . . . Every apartment door seemed to have three locks, including a steel bar that was jammed into a slot in the floor."