Since the international border runs down the middle of the river, diverting the river changes the international border. That would take some serious cooperation between us and Mexico. Mexico would raise objections to any negative consequences to their border towns. Technically, yes we could divert all or portions of the river, but then the enviro-whackos get involved and grind progress to a halt. It’d be years before any meaningful progress was made.
Sort of impractical but possible.
To a Liberal, we could then use the argument, “look at all the shovel ready jobs this would create!”