I suspect cost wise you are going to be better off just tossing your USB camera and buying a IP camera. You are just past the limit for some of the more inexpensive devices. The main thing that causes problems even when you are closer is if you require the USB to power your end device. It is easier to extend the data signals than the power.
They do make devices that will carrier USB over 100meter ethernet. These are active devices that require power on both ends. They are much more expensive than just buying a inexpensive ethernet connected ip camera.