Corsica has been French for only 210 years in its 3000-year history.....
Corsican culture is more similar to Italy than to France. In fact, when the French wanted to crush the Algerian FLN, they used the Foreign Legion and Corsican conscripts in the French Army rather than mainland Frenchmen.
Napoleon was born in Corsica when Corsica was part of France.
"French" is not a race, but a national identity. Napoleon, as a French man, was educated in French military academy and always served the French military.
What is your point? That Napoleon's being a Corsican means that he was not Emperor of the French, or French, or that the Grande Armee and its achievements and failures were not French?
What is the reason for taking that line?
It's very strange.
George Washington was not a native born American citizen. He was born a British subject. Indeed, every US President before John Tyler was born an Englishman on British soil, and was an Englishman until America shook off Britain and became independent, thereby naturalizing all of the native sons of America as English.
It would be a very strange thing, however, to call Washington, Adam, Jefferson, Madison, Monroe, et al Englishmen or British, even though they were, technically, until independence anyway.
I don't understand the significance in Napoleon's birthplace being Corsica as opposed to, say, Normandy or Brittany, Alsace or Poitou or the Ile de France. What difference does it make? "French" is all of those things. When Napoleon was born, to be born in Quebec was also to be French. Nobody FRENCH disputed that. Certainly Napoleon did not need to obtain some sort of waiver from his King to attend French military academy, given that he was as French as anybody else.
Corsica has its regional peculiarities. So does every other region in France. The culture of the Val D'Aosta is very Italian, as is the culture of the Cote d'Azur near Italy. Marseilles is very different from Paris, and yet the national hymn is the Marseillaise, and not the Parisienne.
I fail to understand the regional significance of Napoleon's birthplace, other than as a point of color.