Erm...region changing isn't going to solve your problem. Lemme think how to explain this...
Wii's are split up into different regions in order to prevent earlier sales, different region televisions and things like that. (retail) PAL games aren't supposed to run on NTSC wii's and vice versa. The fact that yours does already means that you have some sort of hack in place that'll circumvent that region restriction (I may be wrong, but I think USB loaders just load any game, no matter what region).
It is true that the wii has different channels per region (including the system menu)...but once the game is loaded, it does not check those versions whatsoever. It isn't a sort of operating system that handles the game...if the game is run, it is ONLY the game that is run. So the region of the system menu doesn't matter. In fact: priiloader actually "overwrites" the system menu (it actually uses its memory location...the system menu itself gets written to another address).
So...you can region change your wii all you want...but it is not the actual issue that prevents black ops from going online (unfortunately, I don't know what the real problem with that game is).