This article accompanies the fable
The land of Barsoom (Mars) is divided into different races just like Oz - with red, green, white, yellow and black races, with each having particular characteristics. For example the reds are the good guys, the greens are the savages (one of them is shown below). Burroughs' worlds are much more dystopian than Baum's, which Burroughs regarded as children's stories, though he got on well with Baum when they became friends in Los Angeles some time between 1913 and 1916.
Besides the Baum's books, there are echoes here of previous fanciful speculation by Percival Lowell about life on Mars and canals across the Martian landscape, as well as the on-going search for lost worlds, mostly in South America. Machu Picchu was "discovered" by westerners in 1911 and Sir Arthur Conan Doyle's The Lost World came out the following year. Burroughs'
tackled the subject himself with The Land That Time Forgot in 1916.