I mean, that's also a result of actual geopolitics. India and China are, here, now, unified, and Europe is not, so there's an assumption that India and China are naturally unified civilization, and Europe is not.
The Arab world is a bit of an exception, but the Arab World a)was famously united for a long, long, long time and b)is often lumped together in popular perception in a way almost no other part of the world is.
But China, unlike India, Europe, or the Islamic World, has a long history of an inertia toward unity, even in periods of sharp division. The Mandate of Heaven from 221 BC to AD 1911 has always gravitated the nation back toward unity - a unity that became politically and cultrually natural, and was a cornerstone of Classical Confucianism. Even when Puyi, the Last Emperor of China, abdicated in 1911, and Sun Yat-sen, Li Anhui, and Yuan Shikai declared the Republic of China in 1912, and formally abolished the Mandate of Heaven (though Yuan declared his own putative Imperial dynasty for eight months between 1915-1916, and Puyi and was made a puppet Emperor of the Japanese proxy state of Manchukuo from 1931-1945, and also declared the revival of the Mandate of Heaven, but these two, what are called in Monarchial circles, acts of pretense). The Republic of China, under Sun, Li, Yuan, and later Chiang Kai-shek, declared, nonetheless, even without a Mandate, all of China as a unity, singular, and indivisible nation - and even though none of those leaders ever de facto controlled Tibet, Xinjiang, or Mongolia, (or Tuva, which is now part of Russia), which had been vassals to the Qing Dynasty of China, they viewed them as integrall parts of the new Republic, and planned on, "subduing," them when wars with Warlords, Japanese, and Communists. However, in the end, the Communsits won, on the mainland, in 1949, and Chiang's party and government, the Kuomintang (or Nationalists), fled to Taiwan, where there descendents, and the same government (even if it's become democratized from a former brutal military dictatorship) still remain to this day. Mao Zedong also viewed China as united, singular, and indivisible, also even without a Mandate. And, both Beijing and Taipei (though the latter a LOT less vocally, today, but it's still OFFICALLY there, ON PAPER), claim to be the legitimate government of all of China, as a unified, singular, and indivisible whole. Thus, the gravitating theme of unity is much stronger in Chinese history than in European, Indian, or Islamic history.