You're definitely right about Native-American culture still
being underrepresented. I think I'm a bit skewed by the drought of sites the U.S. had during the 80s/90s. I am really positive about Hopewell and Serpent Mound. I hate calling it "Montezuma's Castle,"
but the 12th.-15th century cliff dwellings in Camp Verde, Arizona are different than the much earlier sites that have been inscribed (Burial Mounds, etc.) Is it too close to Taos Pueblo or Chaco Culture? However, it represents Hopi and Yavapi cultures who to my knowledge have no representation. URL
Fantastic monument and these are underrepresented Native American cultures from the late-period.
edit: Another interesting addition would be a serial nomination of Navajo monuments. Sorry, I changed it from Anasazi (part of Chaco/Pueblo culture) to Navajo, which is distinct. Places like Monument Valley, Little Colorado River Gorge, Grand Canyon (ofc), The Hubbell Trading Post, Grand Falls, El Capitan, Elephant's Foot, Antelope Canyon, and Canyon de Chelly. Some of these could be inscribed alone - but a Navajo Nation Serial Nomination
would be incredible. It would stretch from hundreds of millions years of natural heritage, sacred ground to Navajo, to the Hubble Post (oldest continuously operated trading post in the U.S. ) to the present.