This tells the story of a vaudeville comedy act, a husband and wife team, booked on the Ed Sullivan show, on the day that The Beatles made their American debut. They were completely blindsided. They didn't have any comprehension of what was happening until they were in the middle of it. They didn't really get it until later. The story includes an encounter with John, surreal for the juxtaposition of the ordinariness of the interaction, and the symbolism -- these two completely different eras encountering one another without any awareness of what was represented.
To push the point too far maybe, what was changing was the very sound of life in the US. You hear these old timey comedians, and they have the rapid fire delivery, the tone of voice, the corny jokes, the style that characterized vaudeville and TV sitcoms. And then you have The Beatles, ushering in something brand new (to the vast majority of Americans). I think it's the same sort of difference you see in movies: Before the mid or late 60s you had this very stylized and artificial way of speaking, often with this weird and phony "mid-Atlantic" accent. And then you had much more realistic movies and ways of speaking, e.g. anything from that era with Jack Nicholson.