JUST UPGRADED TO MONTEREY 12.0.1 - DUPLICATE FILE COPIES ON USB STICK KEEP SHOWING UP

Presumably NTFS or FAT.

macOS is going to create some hidden files for Finder data, and potentially for other activity depending on (for instance) the apps in use.

If you want to see the hidden files in macOS Finder, Command-Shift-Period is the hidden-file toggle. (The following is for a volume named USB. Change the label as needed. Since this is the shell, escape any spaces within the volume name with a backslash \. /Volumes/A\ B\ C for a volume named A B C, for instance.)

sudo mdutil -i off -d /Volumes/USB
defaults write com.apple.desktopservices DSDontWriteUSBStores -bool true

The dot_clean tool can be your friend, too:

dot_clean /Volumes/USB

See man dot_clean for details of what it clobbers.

The BlueHarvest app might interest, too.

This is what was referenced earlier, can’t be entirely disabled, and marginally manageable from Windows. You can reduce the creation of some files as was described previously, but macOS apps including Finder are still going to write those metadata-related files where Windows can find them.

While you’ve not seen these hidden files on FAT or such before, dot files are far from new.

Windows 10 has a means to disable that display with the attrib command, too. Sort of. Though it seems attrib applies to existing files, and not to newly-created files. Which means it needs to be re-run. The link goes to a hack which re-runs the command.

https://albertrtk.github.io/2020/10/04/Hide-files-and-directories-that-name-starts-with-a-dot-(on-Windows-10).html

https://windowsloop.com/attrib-command-to-hide-folder-windows-10/

HFS+ is the native file system, and inherently supports the storage of the metadata being recorded here.

So you won’t see resource forks and other data on an HFS+ volume, though you will find .DS_Store settings file in any directories visited with Finder.

Microsoft FAT does not support resource forks and related metadata storage, and has always done what you are encountering here when used with macOS; the creation of these (hidden on macOS) dot files.

If you’d like to see the hidden dot files on macOS, use the Finder chord Command-Shift-Period to toggle the display.

Want to see a whole lot more hidden files on your Mac? Go to your home directory in Finder, and use the Command-Shift-Period chord to toggle hidden-file display there. On a typical Mac, you’ll find hidden files. Often lots of them.

Run some web searches, and you will find many previous discussions going back a decade or more with macOS and OS X.

Dot files as hidden files for metadata and for settings go back ~forty years on Unix, and on Linux, macOS, illumos and other Unix-influenced or Unix-descended systems.

Welcome to knowing a little bit more about the operating system and the file systems you’re using.

The #1 (problematic) USB format says MS-DOS (FAT32).

The #2 USB format says Mac OS Extended (Journaled).

As I stated before, it will happen on all FAT formats because that file system cannot handle metadata attached to the file itself.

Seems like a lot of trouble to fix something that wasn't a problem before.

The fact that you were unaware of it doesn’t mean it didn’t happen before. In every macOS version, metadata files are written to file systems that are incapable of transporting the metadata with the file (for the most part, all FAT file systems).

Please post screen shots of what you’re reporting, then. One from Windows, and one from macOS.

What is the file format of the other drives?

Did you copy files to them via the Finder or something else?