The American folk revival scene took notice of the Beatles success, and within a year or two of the Beatles' arrival in the U.S., artists like Bob Dylan and The Byrds ditched their acoustic instruments and went electric, inspired, in part, by the Beatles.
This influence went both ways. While the Beatles had initially been inspired by American acts like Elvis, Chuck Berry and Little Richard, the U.S. music scene continued to have an impact on them and other British bands. "The interchange the between the British and American music scene – which was non-existent at the end of 1963 – was huge within a year, a year and a half," Unterberger says.
When the Beatles met Bob Dylan in person in August 1964, he notoriously introduced them to marijuana, sending the Beatles on the path of drug experimentation that would manifest itself in the evolution of their music. But Dylan also spurred Lennon's growth as a songwriter. According to Thompson, Lennon was always a poet interested in weird word combinations, but hadn't thought to use them in his pop songs. "Bob Dylan -- one could rightly say -- all he did was wake John Lennon up to that fact."
From The Byrds exposing Harrison to Indian music to the echoes of The Beach Boys' monumental album "Pet Sounds" heard in the Beatles "Sgt. Pepper's Lonely Hearts Club Band," the Beatles' musical trajectory would have been unthinkable had they not broken down the wall between the American and British music markets.
The relationship the Beatles had with their U.S. audience transcends any individual song, album or even the effect they had on entire musical subgenres. According to Wald, their entrance into America represents a crucial transition in the development of American musical pop culture: Americans began to prefer dancing to recorded music instead of live bands, and the term "rock 'n' roll" was no longer synonymous with dance music.
"Up until the Beatles there is no rock band that isn't making dance music -- that simply was what rock 'n' roll music was. And when the Beatles start out that certainly true of them," Wald says. "But they evolve rather quickly. By 'Rubber Soul' and 'Revolver,' they're not playing dance music anymore."
This shift had implications in both the racial and gendered attitudes towards rock music.
"When The Beatles first arrive they're playing music that girls are dancing to, and by 'Revolver' and 'Rubber Soul,' they're playing music that boys are sitting around and talking about, and feeling like they are smarter than the stupid girls who were going dancing," Wald says. This musical division would continue: For instance, discos became the home of "girly" recorded dance music, while the punk live music scene that would later arise would be seen as more masculine, and thus to be taken more seriously.
But at a time when racial barriers were coming down, the Beatles inadvertently re-segregated pop audiences. Before the Beatles, guitar groups had been on the way out in America, with teenage girls flocking to Motown and soul singers like James Brown. "A huge part of what was happening is that popular music was going black," Wald says. "For a lot of people that was scary, and the Beatles were whiter than white," even though the Beatles themselves counted black rhythm-and-blues groups among there most important influences.
When the Beatles returned for their third U.S. tour in August 1966, it would be their last, anywhere. By 1969 they would call the quits entirely. In some ways, the Beatles' success in America spelled the beginning of the end for them – and not necessarily because of Yoko Ono (she and Lennon met in London, after all). "A lot of people would like to over-play Yoko Ono's role in the breakup of the band," Thompson says. "They were going to break up anyway. They were maturing. They needed to move on to something else."
Some of that maturing was personal, but much of it was creative. The blending of international music scenes sparked in part by the Beatles' American arrival also brought about the band's own remarkable music evolution in the years that followed. But when the Beatles evolved to the point that they could no longer make music together, it also meant they had millions of American fans mourning their break-up.
Corrected, 1/24/14: : A previous version of this article misquoted Elijah Wald on the meaning of the Beatle’s success in America. He said, “Every British rock ‘n’ roll band before the Beatles had been considered just a simulacrum of American music.” The article also misidentified Gordon Thompson. He is a professor at Skidmore College.