That is not true. Japan, China and Korea were nations for centuries before nation states formed in Europe. These countries has a strong central government. And any government that come afterward would inherit the mantle of the previous government. In these three countries plus Vietnam, there are succession of dynasties, Or military government, the shogun, in the case of Japan. So these countries would form a single national state without a European nation create it for them, as in the case of India.
Are you saying that if for some reason, India is capable of doubling its size in the next ten year, than India today does not exist as a nation?
China's borders were self-marked by the so-called "great wall" ... china is now the last country practicing colonisation over Tibet, Xinjiang and Inner mongolia, after South Africa gave up its colonial rule of Namibia.
PRC should peacefully withdraw from Tibet, Xinjiang and Inner mongolia so that colonialism is finally wiped from the face of the earth.
Learn from South Africa, how they peacefully withdrew from Namibia.