NEW YORK — Even the Beatles didn’t quite comprehend what awaited them in New York on Feb. 7, 1964. Six days after “I Want to Hold Your Hold” broke through as their first No. 1 hit in the U.S., Paul McCartney, John Lennon, Ringo Starr and George Harrison braced for a warm welcome as Pan Am Flight 101 out of London neared its destination in Queens. Never, however, did they expect the spectacle they found when they disembarked. Some 3,000 fans, many of them smiling, shrieking, hysterical girls who skipped school on a Friday, ambushed JFK Airport, congregating along the rooftop and pushing past po…