The American Southwest has horribly mismanaged it's fresh water supply. Tulare Lake, Hoover Dam, and Las Vegas are just some examples of the American Southwest's horrible fresh water management. My suggestion is does the rest of the United States and North America have a right to the fresh water contained in the Great Lakes? Would a pipeline from Chicago to Los Angeles or Mexico City be better for the environment than a desalination plant?
The amount of water usage for personal use is a tiny fraction of the water usage in those states, and there is still far more than enough water in those states to surpass all of the personal use for as much water as you can drink, as many showers as you can take, and as many loads of low-efficiency machine laundry you could do. Let's just use California as an example. No more than about 11% of the water usage is "urban uses" which covers all the water you use in daily life plus all industrial use. Between 30 and 50 percent goes to agriculture (more than half of which is exported) and about a third of the overall water use is Pistachios, Almonds, and Alfalfa.
Alfalfa's issue is not that it's a water-inefficient plant, it's actually very water efficient, but that it's borderline useless for anything other than feeding to livestock. There are lots of issues with animal agriculture, but arguably one of the most important ones here is that farmers in the US don't actually even feed their livestock alfalfa. They feed them grass, corn, bulk skittles, whatever's cheapest, and that's not alfalfa.
Pistachios are terribly inefficient for areas like California, but are super profitable. They're also a fairly significant driver behind the "war with Iran" lobby, as Iran is the other main top producer of Pistachios (and also their native area, along with Afghanistan.) They grow in areas that have no freezes, need low humidity, and a lot of water, so they can primarily only be grown in irrigated areas which works great when you're right between the ocean and a massive freshwater(ish) sea like the Caspian with twice the combined volume of the Great Lakes and have a population of about 3 million like the Kerman Province in Iran where most pistachios are grown. It doesn't work as well when you're also trying to grow a shitton of other crops and also have a population of 40 million (6 million of which are in the growing area and competing for water) going after the same water source.
Almonds are a nightmare, and those grown in California use more water than all non-agricultural water use in California and Nevada combined.