Recently, it was debated in political circles that India is not a nation but a union of states. There are many who believe that India as a nation emerged recently and is a consequence of the British Raj and subsequent independence movement. This idea of Indian nationalism is European centric which predicted during the independence of India that India will fail as a nation as it does not share a common language which is the basis of European nations.
The language criterion for the definition of the nation narrows the concept of nation. India survived against all odds even when regional and foreign vested interests were in play for separatists. The word nation has a European origin with Latin and French roots. Certainly, the concept of the nation would have different terms in different languages around the world. Every Hindu knows about the religious significance and medicinal importance of the Tulsi plant but they hardly know that it is the Holy Basil plant or Ocimum sanctum, does this mean the Hindus do not have the concept of Holy Basil!
Before diving deep into the concept of India as a nation, it's important to define what is a nation in its broadest sense and before this, it's important to highlight what it is not.
As a concept, a nation is not a country which is a geographical entity. A nation is not a state, an empire or a kingdom which is a political entity. However, a living nation constitutes a country, a state, or an empire. For example, Israel is a nation which once does not exist as a country and a state when it was under the Ottoman empire but the nation existed in the hearts of the Israeli diaspora around the world which reclaimed its country and the state.
The nation is the bonding between the people for achieving a common goal and expressing a sense of security.
I don't care whether the English word nation conveys this meaning or not. For me, this is the essence of the word "Rashtra" which is used across all languages in India. The students and thinkers of social science and political science are confused with the notion of Nationalism. For some, it is a positive notion for others it is a negative notion and many use the term as their convenience.
India is a Rashtra (nation) from ancient times. The Goddess Vak-Ambhari declares in Rig-Veda which mentions in Devi-Suktam "Aham Rashtri" and from here originates devotion to the Bharat Mata (the Mother Bharat). The motherhood of the nation provides a sense of security to all its children. Nationalism is an emotional entity; when the emotional flux is towards God, nationalism becomes a spiritual entity.
What makes Bharat (India) a nation? The common struggle of its people to achieve ultimate freedom makes Bharat a Rashtra. The twelve Jyotirlingas, fifty-two Shakti-peethas, four Dhamas, four Mathas, footmarks of Sri Rama from Ayodhya to Rameshwaram, footmarks of Bhagawatapada Shankaracharya from Kaladi to Kashmir and footmarks of millions of pilgrims every year marks the boundary for the country for the Bharat Rashtra. Where the Dharma rules according to Shruti and Smritis and if the ruler becomes wicked, God comes Himself to establish the rule of Dharma, forming the state for the Bharat Rashtra.
Whether it's Ghadar in Canada and the USA or Indian National Army in Japan and Germany during the Indian independence struggle has proved that the Bharat Rashtra is not confined to a landmass, it lives in the heart of the children of Bharat Mata. They reclaimed the country with unfortunate partition and the state with an unfortunate secular constitution.