busyFirst, look at the damage done to western ecosystems by water extraction. It has all but destroyed the rivers and their anadromous fish, once the richest ecosystem of Turtle Island. The Mississippi River has enough challenges from humans walling off its floodplains; it doesn't need to be drained of water on top of that.
Second, infrastructure is expensive and it fails. Build it now, cover up the problem of water shortage, and that just makes matters worse 5-10 years down the line when the system starts needing significant repairs. And America loves building but hates repairs, so you can expect a water system to reach the shitty condition of the roads and bridges in very short order.
A civilization must live within its water budget. That means each region gets only what its rain, rivers, etc. can provide. If you don't like the restrictions, move somewhere with more water, because there is only so much that technology can do to cover up the shortage.
Things that would actually help, that people don't want to do:
* Ban commercial drainage of aquifers. Reserve that for local use.
* Stop watering lawns, golf courses, and everything else.
* Reforest the uplands to store water from seasonal rains and release it through year-round runoff.
* Only grow crops whose water needs match the availability of local water resources.
* Encourage people to move from low-water to high-water areas.
* Study measures in other countries to conserve water, since America uses several times as much as the more frugal countries do.
