Whitworth is as standard as threads get. It was the very first standardized thread: Witold Rybczynski's history of the screw and the screwdriver, "One Good Turn", gives the story (before Whitworth, each bolt and its matching nut were hand-made in pairs). It is still the standard thread for camera mounting bushes, worldwide (1/4" for the smaller ones, 3/8" for heavy-duty stuff like large format cameras). I'd bet it's still used in the US for hinges on agricultural doors and similar applications.

I have never found out what the thread is on the neck bush and lyre mount for my 1922 Buescher True-Tone C melody sax. The butterfly head broke off the threaded shaft, and my repairman had to braze it back together because he had no more idea than I did where to buy a new one. What threads did they use in the US in the 1920s?