I'm interested in the US military presence at Iguazu - can you post a link with more info?
Regarding fresh water sources, wouldn't the Great Lakes make more sense as a water source since they're local to the US? Wikipedia says, "The Great Lakes are the largest group of freshwater lakes on Earth by total area and the second-largest by total volume. They contain 21% of the world's surface fresh water by volume." Source:
https://en.wikipedia.org/wiki/Great_Lakes
For underground water specifically, when I ask Google, "
what is the largest underground water source in the world", it says, "The Great Artesian Basin in Australia is the world's largest underground water source, or aquifer"