Is it possible to replace the USB port/controller?

So, basically, what you're saying is, that my USB controller is OK, but if even just the outlets/sockets are corroded that would be such a huge issue, that I couldn't be able to replace them myself? How about something like this: http://www.youtube.com/watch?v=0Lx0NSXQZ...

You need to take power sources away from it (battery, etc...) and clean up after the liquid damage. Yes there is only 1 USB controller. However, the USB controller has 4 channels operating 8 deices (2 per channel), without looking at the schematics I couldn't tell you if both ports are on the same channel, though I doubt it. It is possible for 1 channel to be bad on the USB controller and the rest to function properly. The USB specification is about data transfer rate and not about amperage to power or charge something. Please tell us more about the devices you have attempted to hook up to the USB port(s). On the USB ports there is, among other things, a 15K OHM resister that creates the amperage for the port (on all the Apple motherboards I have inspected). It is a 402 SMD package, less than 1mm in length, and you really need a stereo microscope to solder it in. The actual physical port you attach to is a rarely at fault without it being physically damaged to the point of not passing visual inspection.

Unlike the vid in your reply the Apple logic board has a lot of SMT components near the sockets that a heat gun will disturb. Focus on cleaning the soda spillage and then see where things are. One thing I did forget to ask is your USB device/s powered or unpowered? As ABCellars pointed out your USB I/O could be OK, but, the power side of the port could be damaged. Try a powered device or hub to see if thats your problem.

Dan is correct, work on cleaning the board - properly, rather than how to replace parts. I did not notice the link to a video until Dan pointed it out. DO NOT, I repeat, do not follow this persons procedure. He does not use any heat tape or shielding to protect the components around the ports. Then he makes an even uglier mistake by shaking the board after it has been heated. The latter can cause other components to be moved from their position, causing even more problems. With the damage being caused by soda you may have to clean the board several times to get rid of the contaminates, especially since it has had a chance to dry. Also as Dan stated try devices that have their own power supply to help narrow down the nature of the problem.