the USB port gives you a connection to the router's board and operating system - if that doesn't know what to do with the device it sees then nothing will happen.
Chances are the router is running Linux and makes a plugged in hard disk available as a shared file store, or a printer as a shared printer. No idea what it would do with a camera, best to RTFM for a router with a USB socket and see what services it offers.
I don't believe a USB webcam has a TCP/IP connectivity, it needs a driver in the OS to work with it and provide connectivity and services.
MaxDSL - goes as fast as it can and doesn't read the line checker first.