Why don't more homes in the U.S.?
While you could potentially save a lot of money on heating and cooling by putting your house under ground, theres a lot of disadvantages to it: Access is cumbersome, climbing down stairs to access your dwelling. The views are pretty damn boring since there are none. Moisture and dampness will almost inevitably penetrate into your living quarters, likely causing molds to grow (which can actually be deadly in some cases). Im sure there are plenty other good reasons too its of course no coincidence that most cellars are used for storage and such, rather than living. Modern buildings in developed countries will typically be rather well insulated. In Denmark, when constructing new houses or renovating old ones, theres a requirement that insulation is some 40cm in the walls, iirc. Thats quite a lot, and will provide equal amounts of heat savings as putting the house underground would. Instead of putting it under ground or using modern insulation above ground, you could just make your walls of one meter thick earth or so to achieve the same objective but whod wanna live in that??? Some places, they construct the inner walls of two inch steel which is pounded deep into ground the idea being that the steel will transport heat from the ground up into the house at winters (and vice versa at summers).