This came across my Twitter feed yesterday.

Hillary Kelly is an American journalist, identified on her Twitter bio as a Philadelphia native. “Knob,” according to the OED, has two groups of meanings. The first, used both in Britain and America, refers to “A rounded lump or protuberance, and related senses.” The second, mainly British, refers to a penis, literally and figuratively.
The first literal citation is from 1922. Martin Amis used it in 1973 in The Rachel Papers: “My knob was knee-high to a grasshopper, the size of a toothpick.”
The first figurative citation, denoting “An annoying, unpleasant, or idiotic person (esp. a man or boy),” interestingly, is from 1920. All the examples are from British, Irish or Canadian writers, an example of the last being Douglas Coupland in his 1991 novel Generation X: “I’d made all these plans to meet before, but he kept breaking them, the knob.”
And by the way, here’s a video giving the varying pronunciations of the word:
It’s hard to search for frequency of this sense of the “knob,” since there are so many others. I chose to search for the phrase “such a knob” on Google Ngram Viewer, and got this result:

For the same reason outlined in the paragraph above, it’s hard to quantify American uses, besides Kelly’s, of the insult. My best luck was with the tool in Tweetdeck that lets you search for tweets including a word or phrase that have been sent from a particular location. I chose a 200 km radius from New York City. There was a good bounty, surely because so many knobs have been acting knobbish in this country in recent days.
This one is from Western New York:

And this from the Adirondack Mountains of New York:

Then there’s this one, from Rhode Island, that suggests new avenues for research:
