Bottled water is indeed pure of the goo, which is why you still have things like scientist and military corpses lying about; they hadn’t been drinking the goo-infested water and were therefore immune to reassurection after death. It’s widespread enough that you are pretty much limited to pre-Cata sources of bottled water though, which is a lot but not unlimited.
As for filtering I wouldn’t be surprised if some part of the goo has developed in such a way to emulate the properties of water that allow it to penetrate through graphene. The goo is constantly developing new mutations and passing on the useful ones to other parts of the goo, so it wouldn’t be surprising if the ability to emulate water turned up and proved useful enough to pass on for some reason or another.
I probably wouldn’t rate any particular bit of water in the ocean as sentient, but with the sheer amount of volume I wouldn’t be surprised if the ocean as a whole started to develop a vague sense of consciousness.
I could see a potential hijacking of the goo mechanisms to stop an infection, though since the adjustment happens pretty quickly after the initial infection you would probably need to be treated immediately or go the route where you treat yourself with a bit of the stagnant goo to trick active goo from infecting you, but not enough to actually trigger the ressurection. And it would always be vulnerable to a countermeasure being developed by the goo (constantly replacing that 1% with any new goo ingested and passing out the old goo instead of having the new goo pass through?)
On the topic of other countries, while It isn’t known right out if any other countries were experimenting with portals or had networks as extensive as the U.S.'s, IIRC it was definitely suspected that several others of the larger countries were also researching them and working on setting up their own networks.
