Hi,
interconnection between two PC's via USB is based on TCP/IP. It's not ordinary wiring. And available products are very slow, about 6Mbit/s. Theoreticaly it could be possible e.g with two PIC 18F4550 and using parallel. But this is madness, I think.
This is only one complete solution which i have found: **broken link removed**
https://www.usbgear.com/item_143.html
# USB host to host communication
# TCP/IP ,NetBEUI, IPX/SPX
# Maximum Data transfer rate: Over 5 Mbps.
# Construct USB Network up to 17 PCs
Price=$39.50
And 3rd, in case one of your PC has an Ethernet port. https://www.usbgear.com/item_130.html
The USBG-110T USB Ethernet Adapter provides an easy way to connect a USB-enabled desktop or laptop PC to a 10/100BaseT Ethernet LAN. It comes with an attached USB cable that has a type A plug for standard USB connection to PC's USB
Price=$33.50