USB cable cut past branching?

Assuming you have both ends you should be able to use wire cutters or utility knife to remove the outer wire insulation from both ends about an inch long , you will have to do the same with any smaller wires inside then connect the same colored wires by twisting them together and using a wire adhesive or electrical tape to cover the wires so they do not contact each other and then wrap the whole join with electrical tape. If you have heat shrink wrap on hand you can use this but you will have to put it on the wire before you join them as it will not fit over the usb connector.