A leading preoccupation of the first Trump administration has all but slipped from view. Except when ostensible conservatives speak out against it, the major media have scarcely breathed a word on the subject. But it’s still there, 30 feet tall, aspirationally 1,952 miles long, obliterating habitats, dividing families and sucking down public funds faster than a carrier-based air squadron. The media’s lack of attention is understandable. All-too-…