Why does Perrie Aronnax seem obsessed with the nationality of everyone he meets?

In part, Aronnax is obsessed with other people's nationalities because of the pervading sense of European superiority at the time. For example, he says of Cunard, a British shipping line, "No ocean-going company has been run with greater skill; no business crowned with greater success." In an age of colonialism and sea power, he believes in the right of Europeans, including Frenchmen like himself, to exercise control over the seas. Against this backdrop, even research...

In part, Aronnax is obsessed with other people's nationalities because of the pervading sense of European superiority at the time. For example, he says of Cunard, a British shipping line, "No ocean-going company has been run with greater skill; no business crowned with greater success." In an age of colonialism and sea power, he believes in the right of Europeans, including Frenchmen like himself, to exercise control over the seas. Against this backdrop, even research into the mysterious monster observed on the sea acquires political dimensions. He says, "after research had been carried out in Great Britain, France, Russia, Prussia, Spain, Italy, America, and even in Turkey, the hypothesis of a submarine Monitor was rejected once and for all." He is embroiled in the scientific controversy not only as individual but also as a representative of France. 

Aronnax is also obsessed with nationality because he cannot determine where Captain Nemo is from. Nemo's origins, though he speaks French fluently, remain a mystery throughout the entire tale. Aronnax tries to understand Nemo by determining where he is from, but Nemo defies any categorization. For Aronnax, who believes that each nation's people have their own character, this is deeply disturbing. The idea that a person is not from a particular country does not fit into Aronnax's colonialist and Eurocentric view of the world.