Quite apart from the concurrent USB device connection limit of 127 devices at any one time (by which time you will long have run out of available drive letters), I suspect you're going to quickly run into the Windows 'USB enumeration' bug whereby the registry has a limit of how many enumeration records it can hold of USB device connections (i.e. time, date, hub, port, device type [e.g. 'mass storage'], device name, PID/VID, manufacturer, serial no. [if present], transfer speed and other capabilities [e.g. hot unpluggable], etc.).
The problem is that Windows records
every connection of a USB device (even via a 'passthrough' device like an external USB hub) and stores the info away in the registry... but never, ever removes the information, even when the device is disconnected. As such, they're classic registry artefacts that forensic investigators rely upon (much like 'ShellBags' entries since Windows 7). Even if all you do is move a USB stick from one USB port to another, a whole new set of entries is collected and stored... even though the only real hardware 'change' is the port used.
Once the (un-documented) enumeration limit is reached you'll end up increasingly with 'Unknown Device', 'Device not recognised', 'No drive letter assigned' or perhaps just the Windows 'Connect' sound but no appearance of the USB stick in 'File Explorer'. Once that happens you'll have no option but to start clearing out the contents of the
USB and
USBSTOR sub-keys under
HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Enum\ used to store enumation info.
Google something like
Unknown USB Device (Device Failed Enumeration) to get a better idea of the scale of the problem... and note that the bug
doesn't just affect Windows 10/11 as many of the results suggest. Note also that many of the results incorrectly point the finger at corrupt USB drivers (?), missing 'Windows Updates' (?) and even mainboard issues (?).
AFAIK the USB 'enumeration limit' bug is solely a Windows issue, was introduced with Windows Vista, has
never been addressed by Microsoft and has become more noticeable (and reached quicker) now additional info about USB3 (driver/transfer speed/capabilities, etc.) is stored. It's even worse if you're configuring multi-capable devices like SatNavs or Apple iPhones, iPads and iPods as these have multiple modes and store far more registry entries per device.
As a result, the only effective 'fix' I know of is really just a temporary workaround... the issue
will re-occur at some point in the future as more USB devices are connected/disconnected. For example, see
this post from two days ago.
Hope this helps...