So who came to the rescue of the depressed United States? The Beatles.
Before they were well known in US, the Fab Four was very famous in the England. On November 4, 1963 Royal Variety Performance, sponsored by the Royal Family, featured The Beatles. The showed highlighted various forms of entertainment, including comedy, drama, and of course, music. And The Beatles stole the show. The group went onto do few other musical concerts in England. When their performance is not the last on the setlist, audience left the concert upon the departure of The Beatles, without waiting to see the rest of the setlist by other actors. This led to The Beatles highlighting concerts at the end. They were also quickly becoming quite popular.
At the end of 1963, one of The Beatles' songs charted in US. Brian Epstein didn't want to tour the US without a "hit" single. I don't exactly know the name of this song, but I think it was All My Loving. By February of 1964, "The Beatles are coming" was the common phrase on the street. The band received a massive publicity. There were countless TV and radio ads, Beatles merchandize and magazine articles.
It's hard to put a finger on one specific incident and state it as being solely responsible for considerably changing the course of human history. The appearance by The Beatles on Ed Sullivan's Show on February 9, 1963 did change the course of, not just the history of popular music, but history in general! During their performance, the girls were screaming so loud that people at home watching couldn't hear them. This marked the definitive inception of "The Beatlemania." Two weeks later, The Fab Four had sold over 2 million copies of their albums and over $2.5 million worth of merchandize.
In April of 1964, 12 of the top one hundred songs belong to The Beatles, including the top 5! This had never been done before, and in fact, never has, and probably never will. They were accounted for approximately 60% of all the album sales. They were so popular in 1964, the Fab Four appeared in their first motion picture entitled A Hard Day's Night.
In August 1965, The Beatles performed live at the Shea Stadium. There had never been a live performance of this magnitude prior; thus the organizers had no idea what to except. There were no "cool" lighting systems, no pyrotechnics, no floor seats, no PA systems. All these were developed following this performance.