ALL these decades later, it is still a little hard to make sense of it: Why, 50 years ago this month, did America seem to go slightly bonkers over a boy band from Britain?

It is considerably less surprising that the semi-centenary of The Beatles’ first live performance in the United States has occasioned a bit of a fuss this week, given the group’s stature in western popular culture and decades of evidence testifying to the breadth of its influence.

But all that was unknowable back in February 1964. Even the band members themselves were uncertain about the likelihood of a breakthrough on the other side of the Atlantic, even though the phenomenon dubbed Beatlemania was already evident in the UK and on the Continent. Most of their idols, after all, were American — from Elvis Presley, Buddy Holly and Carl Perkins to Chuck Berry, Little Richard and the girl groups produced by Phil Spector.

Why would consumers of popular music in the US be particularly interested in a British variety of essentially the same product?

It wasn’t identical, though. The Beatles had imbibed a variety of other influences, too. And even in the early years, their range was not restricted to rock and roll. And they wrote their own songs, which was unusual for a group — never mind that one American newspaper derided their lyrics as “a catastrophe, a preposterous farrago of Valentine-card romantic sentiments.”

The verdict seems a trifle unfair, although the initial output of the songwriting partnership between John Lennon and Paul McCartney wasn’t particularly sophisticated as far as the words were concerned. Even so, the pair had a knack for catchiness. And the lyrics weren’t all that mattered. Bob Dylan was profoundly impressed by the “outrageous chord changes.” And then there were the three-part harmonies, with lead guitarist George Harrison — not yet 21 when The Beatles first visited America — pitching in alongside Lennon and McCartney.

Dylan was also knocked out by what he thought he heard in a key verse of The Beatles’ first US number one single, I Want to Hold Your Hand: “And when I touch you I feel happy inside/ It’s such feeling that my love I get high…” When he first met the quartet on The Beatles’ return visit to the US later in 1964, he was flabbergasted to discover that they were unacquainted with marijuana. He immediately took steps to remedy that, and wondered aloud about the lyric, only to be told that the last three words are actually “I can’t hide.”

A few years later, the American academic and counterculture guru Timothy Leary described The Beatles as “prototypes of evolutionary agents … endowed with a mysterious power to create a new human species.” Such hyperbole wasn’t uncommon in the late 1960s, and hype also played a role in America’s initial appetite for the band. But there was another aspect to it, too: The distraction and emotional release it offered to a demographic still reeling from the trauma unleashed by the assassination less than three months earlier of a president who, as he himself put it, represented the passing of the torch to a new generation.

Coincidentally, The Beatles landed in New York on Feb. 7, 1964, at the recently renamed JFK International Airport, to be greeted by a screaming mob of 4,000 teenagers. Two days later, they performed live on The Ed Sullivan Show, watched by what was then a record television audience of 73 million. The tag attached to this month’s commemorative Grammy Salute to The Beatles — The Night that Changed America — nonetheless appears to be stretching it a bit.

But perhaps not by too much. After all, popular music in the US more or less reinvented itself thereafter. The extent to which The Beatles were instrumental in catalyzing the counterculture that distinguished the rest of the decade is debatable, but it cannot seriously be denied that they played a role in ushering it in.

Back in London, their services to exports were acknowledged by the establishment with MBEs the following year. In the realm of popular music in America, they paved the way for what came to be known as the British Invasion. Its success was predicated on the fact that, inadvertently or otherwise, the advance party featured Britain’s biggest guns rather than the light cavalry.

A great deal of talent, charm and Liverpudlian wit went into creating the phenomenon known as The Beatles. The talent is evident in the stupendous four-year trajectory from Please Please Me to Sgt Pepper’s Lonely Hearts Club Band. The charm and wit won over a largely indifferent or hostile American media. But there was also a crucial element of luck. In February 1964, the band happened to be just the tonic that the Americans needed to twist and shout their way out of the Dallas-imposed darkness. The Beatles not only offered the appropriate sound, they served it up at the right time. In some ways, America was never quite the same again. Thankfully.

There was an unfortunate echo, though, of the Kennedy assassination when Lennon was shot dead in New York some 10 years after The Beatles broke up. There was also a degree of irony in the fact that his nemesis in the early 1970s, determined to get him deported from the US, was none other than JFK’s presidential rival in 1960, Richard Nixon.

It is unlikely Nixon was much of a Beatles fan in 1964. The exuberance they reflected simply wasn’t his trip.

Barack Obama, on the other hand, was not yet three years old when I Want to Hold Your Hand alerted the nation to how irrevocably the times they were a-changing. He unquestionably benefited, though, from the aftermath, the idealism that subsequently made its mark.

The Beatles weren’t, by any means, the be-all and end-all of western pop culture. But the rainbow they cast across the 60s hasn’t so far faded away.