They're all a hodge-podge of Asian cultures. There's Chinese, Japanese, and Korean stuff all over, with a smattering of more eXoTiC places like Vietnam randomly thrown in.

and yeah Legend of Korra is just fucking awful in basically every regard

If AtlA is WW2-coded then the general vibe of the Earth Kingdom leadership kinda works: a foreign invader is burning half the country to the ground and they're too busy worrying about internal dissent and politicking to properly mount a defense.

Not sure who Mao and the communists would be in this though.

The Earth Nation in the original series was pretty China coded and not in good ways.

I always thought that to a very small extent ATLA was a liberal "Free Tibet (Air Nation) from China (Fire Nation)!" dogwhistle, despite the opportunism of claiming it was about Bush and the War on Terror, as soon as that finally became unpopular, but it didn't stop me from enjoying it.

people forget this, but there's a whole litany of neoliberal balkanization advocacy groups against china, not out of a sincere desire for sovereignty of nations colonized in the past by Chinese imperial dynasties, but out of a reactionary desire to reverse the development of China (this is the same trick they played with Yugoslavia and USSR, after all). The 400 year old proto-bourgeois idea of Westphalian sovereignty has outlived its progressive nature against feudalism and has become a force of reaction against Socialism for keeping nations underdeveloped and divided against each other and preventing international proletarian solidarity, collaboration, consolidation of power, etc.

So you got "Xinjiang is East Turkestan!" (ignoring ETIM and other reactionary groups funded by the CIA through the NED) and "Free Tibet!" (ignoring that Mao Zedong cracked down Buddhist clerical/monarchist slavery and pedophilia in Tibet) and "Free Hong Kong!" (ignoring that Hong Kong was literally colonized by the British until the late 1990s, and was always a bastion of Capitalism in the region) and "Free Taiwan!" (ignoring that Taiwan is basically a holdout for Guomindang bourgeois nationalist warlords, capitalists and reactionaries who lost the civil war to Chinese workers and peasants, i.e. the Chinese equivalent of neoconfederacy). So all these cries for sovereignty seem to the unacquainted like sincere cries for freedom of nations with their own capital-C culture from Han supremacism, but really, they're just cynical calls for balkanizing China so that the regions lopped off from Beijing's control can be more easily infiltrated by western NGOs and think tanks and intelligence agencies who will of course advocate for the usual capitalist nonsense like privatization, deregulation, austerity, lowering the age of consent, reintroducing child labor, legalizing gambling, bringing in foreign direct investment, flooding them with high interest IMF loans, giving money/weapons to reactionaries, cracking down on labor unions and cooperatives, etc. How do I know all this? They had an established pattern of doing this in the Yugoslav nations, the Soviet nations, and for a long time they did it to Cuba under Batista.