It is pretty clear that Inazuma represents some form of Japan. Inazuma (稲妻) is in reference to the Japanese TV series as well as a character from One Piece.
See Teyvat for more details. Also see Inazuma quests and Enkanomiya.
Tsurumi Island is probably based on Hokkaido and Ainu culture. See Version 2.2 for more details.
With the arrival of Inazuma, it has been noted that the enemies are heavier and not easily pulled and lifted by vacuum abilities such as Venti's burst. For example, the nobushi samurai with heavy armor are hard to lift with Venti's abilities. Is this a coincidence?
Historically, the Mongol Empire was extremely successful, conquering territories almost everywhere across Eurasia. But one of the lands it was unable to conquer was Japan. It is said that the Mongol armies were washed away in a typhoon when trying to invade Japan. Now if Venti is the archon of Mondstadt, is it much of a surprise that the enemies of Japan are not so easily lifted by his abilities?
Of course, there is the other argument. Venti was simply too broken before 2.0. Heavier enemies in Inazuma were introduced to make him more balanced. It is certainly plausible. But yet again many things in Genshin have layers of meanings.
So if Inazuman enemies are harder to lift by Venti's abilities, where does Kazuha, the anemo ronin, fit in Inazuma? First off, Kazuha himself is an outcast who escaped the vision hunt decree of the Raiden Shogun. Kazuha's friend was even slain by the Shogun herself. So Kazuha, while being part of Inazuma, is also a character somewhat outside of Inazuma. He finds refuge in Beidou's ship. And at least historically or symbolically, the Beidou-Kazuha duo promoted by Genshin can be seen as homage to the cultural ties between ancient China and Japan, or specifically the influence of the Tang dynasty on ancient Japan. After all, the Japanese script and much of the shared culture has its origins during the Tang period. And as an added bonus (for those who care about seiyuu culture), Beidou's Chinese voice actor is Tang Yajing, and Beidou herself weilds the Electro element emblematic of Inazuma.
But as with many things in Genshin, there is more than one way of looking at them. Kazuha has a connection to another group of people who have lived in northeast Asia: the Khitan people (契丹 Qidan). The Khitans were a proto-Mongolic people related to the Xianbei and Kumo Xi. Their ancestors lived in northeast China and historically had been part of the Han and Tang dynasties, allying with the Han and Tang to defeat the Huns and Gokturks.
More importantly, the Khitans founded the Liao dynasty (辽朝) in northeast China around the time of the Song. The ruling house of the Liao was the Yelü (耶律) clan. Incidentally, both Yelü and Kazuha (万叶 wanye) contain ye in their names. But that's not all folks: the Song allied with the Jin dynasty to kick the Liao out of northeast China. The Jin dynasty then succeeded the Liao as rulers of the northeast. The ruling house of the Jin was the Wanyan (完颜) clan. Incidentally, both Wanyan and Kazuha contain wan in their names.
The Jin dynasty was founded by the Jurchen people, the ancestors of the Man people who founded the Qing dynasty. Both the Jurchens and Khitans were closely related to the steppe and nomadic/semi-nomadic people, emblematic of Kazuha's anemo element. There are some differences in culture and language: the Mongols are more nomadic, whereas the Man initially did more hunting and fishing, only later becoming more nomadic when establishing the Qing.
So in one sense, Kazuha is related to two ruling houses of the Khitan and Jurchen people (Yelü and Wanyan) and is associated to two empires (Liao and Jin) situated in northeast Asia, besides Japan.
The Liao fought wars against the Song, so this could vaguely hint at the relationship between Kazuha and Ayato.
Moreover, just like how the Liao was founded by Khitan (契丹 Qidan) people, Kazuha originally descends from the Niwa (丹羽 Danyu) clan, with both Khitan and Niwa sharing the character 丹 Dan (which also means pill). Surely this is the reason he is part of the Niwa clan and not because certain writers wanted to make political attacks on specific people.
After the Liao was kicked out of northeast China, they migrated west and founded the Western Liao (西辽) in western China and Central Asia. The Western Liao was only one of several kingdoms ruling over China at the time, but they were still strong enough to defeat the Seljuk empire. The Western Liao was very Han Chinese in culture, practicing Buddhism and retaining the Han Chinese language and writing. The Western Liao was still ruled by the Yelü clan, and some of their later descendants interacted with Genghis Khan and served in the Mongol armies.
The fact that the Western Liao ruled over Central Asia and influenced the development of the Seljuks and western regions may explain Kazuha's EM scaling and connection to Sumeru, the land of EM.
This hypothesis gains a bit more evidence when one considers that Nahida, the archon of Sumeru, is also called Buer (布耶尔 which contains the 耶 ye sound). Incidentally, both Nahida and Kazuha scale with EM. So the history of the Liao connects Northeast Asia with the Sumeru region, from the ronin Kazuha to the Sumeru god Nahida.
Trivia: the Liao dynasty name may serve as the basis for one of the provinces created by the Mongol Empire in northeast China. The Liao (辽) character continues to be part of a placename in northeast China to this day.
Inazuma contains several allusions to the Ming dynasty of China. Narukami is represented by 鸣神 which is pronounced mingshen in Chinese, where shen means god. The Raiden Shogun is called the Grand Narukami Ogosho. She is the archon and ruler of Narukami. She is the Ming Shen or the Ming God. The character 鸣 is different from the 明 of Ming China, but they are pronounced similarly. Genshin does this with a lot of characters. They like to play these kinds of homonym games.
As an extra touch, the main mountain of Narukami is called Mt. Yougou. This is where the Grand Narukami Shrine is located.
But there is a more direct connection. The ideal of Inazuma is eternity or 永恒 yongheng or 永远 yongyuan. The character 永 yong also appears in 永乐 referring to the Yongle reign of the Ming dynasty. Raiden herself often talks about yongheng and yongyuan (ei'en). More references to the Ming are swirled into the mix.
Also Yae's name 八重 is a rearrangement of 重八 Chongba, one of the given names of the founding emperor of the Ming dynasty. Both Yae and Raiden are Electro characters with 90 energy cost bursts. In the lore they have a pretty deep knowledge of each other. And both are leaders of the Narukami Island, Raiden as the archon and Yae as the leader of the Narukami shrine. Put together, if Inazuma or Narukami refers to the Ming, then Yae and Raiden manifest themselves as the Ming rulers.
But there is a twist. As with many things in Genshin, not everything corresponds 100% to reality or history. Indeed, in the Inazuma civil war, the Narukami faction fights against the Watatsumi army led by Sangonomiya Kokomi, the pearl of Inazuma. The pearl is an object that has certain symbolic connections to the Ming dynasty and their emperors. Yet Raiden, the emperor of Narukami, fights against Sangonomiya and the island of pearls. This is not necessarily contradictory as even the Ming itself had civil wars in its history where members of the ruling house fought each other for control over the throne (such as during the Jingnan campaign leading to Yongle's usurpation).
The pearl also has another significance in Japanese history, namely the Japanese bombing of Pearl Harbor. Incidentally General Gorou (五郎) of Watatsumi can be interpreted as a reference to one of Japan's WW2 generals involved with the Pearl Harbor plan, Isoroku Yamamoto (山本五十六). Besides the pearl connection, both Isoroku and Gorou have the character 五 in their name. The connection may seem trivial or not rigorous, but not everything in Genshin is blunt or direct in your face (some things are though).
But going back to things not being 100% the way they appear to be, there is also evidence that Inazuma represents another embodiment of the Yuan dynasty again. This time, Raiden is the god of the Yuan, and Mingshen is only a title. The Kamisato estate is another embodiment of the Yuan, with Ayato, Ayaka, and Thoma. Specifically, Thoma's name in Chinese 托马 contains the character 托 tuo. And tuo also refers to another famous figure in Yuan history, Tuotuo or Toqtoa, the writer of the histories of the Song, Jin, and Liao. Ayato has a certain connection to the Song, so the fact that Ayato serves the Almighty Raiden Shogun and that Thomas (tuoma) tends the Kamisato estate gives certain credence to the theory that the Yuan is truly in power in Inazuma.
It could just be that 'ming' is a cover term, similar to how Wei Zhongxian used an alias during the Ming dynasty to sneak into the imperial palace. Moreover Raiden executed Rosalyn, but the Ming was also infamous for executing people by the masses.
Another connection between the Ming and Japan involves the Meiji era. Meiji or Mingzhi (明治) contains the character Ming (明). Meiji was an emperor who industrialized Japan (with the help of Western powers) and also won the first Sino-Japanese war, thereby gaining control of Korea and Taiwan (which were part of the Qing).
But not everything about Japan is necessarily aligned with Chinese dynastic history. They had an emperor named Meiji, but then later bombed Pearl Harbor. Japan was able to fend off the Mongol invasions, but also invaded the Ming under the leadership of Toyotomi Hideyoshi. And yet again, most of the Japanese writing system and cultural customs originate from China, especially during the Tang era.
As it stands, Inazuma represents an entity very related to Liyue, but also something 'outside' of Liyue. The Mongols and Man people were other northern ethnic groups, but they played a much larger role in Chinese history, eventually becoming Chinese themselves.
During WW2, Japan took over a portion of Northeast Asia, including the homeland of the Man people of China. In history, Northeast China/Asia has been the homeland of various nomadic groups that would eventually take over the rest of Eurasia, including the Mongols, Man people, Turks, etc. even having connections to the Xiongnu/Huns and Saka people. The Mongols themselves descend from the Xianbei people. The Man people founded the Qing dynasty. The Turks took over the Sumeru region, founding empires such as the Ottomans, Timurids, Mughals, etc.
So there is a connection between the electro element of Japan and the Northeast region. Keqing is electro, perhaps a nod to how the Qing was founded by the Man from the northeast. Cyno is electro, and electro plays a prominent role in the Sumeru region through reactions such as quicken and hyperbloom. This could be a nod to how the Turkic people from Northeast China would eventually rule over the Sumeru region after the Tang dynasty.
And lastly, we have discussed how Scaramouche can be an allusion to Liu Che of the Han dynasty and the Xiongnu nomadic element. Scaramouche refers to Raiden as his mother, perhaps a nod to part of the origins of the Xiongnu in Northeast Asia. But also Scaramouche acts as the main boss in Sumeru. We have discussed how this can be interpreted as the Xiongnu/Hun/Turkic force invading the ancient Sumeru region in the past. But in light of modern history, it could also represent how the Japanese empire actually did try (and fail) to invade British India during WW2, considering that Scaramouche is tied to the history of Inazuma and that Scaramouche uses a combination of the electro (Northeast Asia) and anemo (the nomadic steppe) elements.
Ayaka, a cryo user, perhaps symbolizes Northeast Asia's connection with Siberia and Russia, with Snezhnaya being the nation of cryo.