The US does not have a fresh water problem. The forecast for the US WRT water supply is Green for the rest of this century. What the US does have is various regional water problems (ie. a water distribution problem). They are self-sustaining wrt water for the foreseeable future, nearly as solid as Canada is in that regard. They have to figure out how to get water more evenly distributed across the states.
And, recall that the US water shortage are not related to water for drinking, but to water for golf courses, lawns, car washes, pools, etc. Water wars may sound "cool", but they're fiction.