The composer was recalling what he had flown over flying E-W out of El Paso, not any specific 'badlands'. The area is Sonoran Desert and montane in large part, not what are usually called 'badlands' (broken, rough areas), which cover only part of the area. From a plane, it would look like badlands to someone not familiar with the region, although it includes mountains, grazing and arable areas, as well as a large population of Sonoran and montane fauna and flora (antelope and deer to ringtails and lizards, cacti to pines).
Also see post above about the Malpais.