Following the installation of the latest NA Maps (2025_20) on my GPSes AND on my PC, I have uninstalled the previous version of the map (2025_10) from my PC using uninstall a programs from the Windows (11) control panel.
After this, basecamp.exe cannot be found on my PC, it looks like the uninstall of the map deleted a bunch of files in the C:\Program Files (x86)\garmin/basecamp subdirectory, including the basecamp.exe application.
This happened on both my computers.
To fix, I have uninstalled basecamp from the control panel and reinstalled it. This went fine and no data was lost.
Documenting this here if it happens to someone else.