That didn't work, but I did mor research found something that did.
On my Windows 10 PC (on which the USB hotspot is working), I looked under
C:\Program Files\Common Files\Apple\Mobile Device Support
In this folder, there were two subfolders, Drivers and NetDrivers. I copied these two folders and their contents to my Windows 11 PC. Each folder contains a driver. I right-clicked on the .inf file in each folder and selected Install to install the drivers. After that, I rebooted. When the PC came back up, it began using the hotspot on my iPhone connected by USB.
I don't know if both drivers are necessary to use the hotspot, but I do know that the driver in NetDrivers is necessary. My surmise is that the first driver installed Apple Mobile USB Device Driver under Universal Serial Bus controllers in Device Manager, and the second (NetDrivers) driver installed the Apple Mobile Device Ethernet driver under Network adapters.
Unfortunately, I do not know why these folders were present on the Windows 10 machine but not the Windows 11 machine. Perhaps I installed some other product on the Windows 10 machine (iCoud?) that created and populated these two folders with these drivers. Who knows?