I really do not understand what you mean.
Let me quote 'man mount':
All files accessible in a Unix system are arranged in one big tree, the
file hierarchy, rooted at /. These files can be spread out over several
devices. The mount command serves to attach the file system found on some
device to the big file tree. Conversely, the umount(8) command will detach
Now let me quote 'man lsusb':
lsusb is a utility for displaying information about USB buses in the sys-
tem and the devices connected to them.
- 'mount' is certainly not reserved to hard drives. For instance you can mount an ISO image using a 'loop' option.
- if a device shows in 'lsusb', it is connected to it: that is to say the system can communicate with the device, be it or not 'mounted'. My system communicate with its keyboard hopefully, though I do not use the 'mount' command for that purpose.
Now please notice that according to the General Systems Theory - which go far beyond and is a lot more general than computer science - a system's boundaries are defined by the observer.
On that topic read Ludwig van Bertalanffy and Herbert Simon.
But may be I am off topic.
It is early in the morning here, I am awakened and have nothing to do till breakfast, this is my excuse