>>117313
Airbender was starting to undergo an industrial revolution, with the introduction of increasing amount of steampowered devices, such as the Drill, that car thing Azula used in the Chase, the jetskis from the Painted Lady episode, the airships etc. etc. Thus they were heading into a world with steampunk technology, even if they weren't wearing the quasi-Victorian clothes that were associated with the genre (because people are lazy and assume that all steampunk is either American or English-based).
Legend of Korra was deliberately based in a world set in the 1920s and 30s, and the tech there had moved on from the steampowered stuff of Airbender (bypassing the bulk of its implimentation) and straight into a world powered by electricity and petrol (such as the radios, cars, mech, planes etc. etc.) The subgenre this is normally associated with is dieselpunk, and examples of this include Captain America: the First Avenger, Bioshock to an extent, the Rocketeer, Laputa: Castle in the Sky etc. etc. etc.