How is Christopher Columbus considered Italian if Italy wasn't a country until 1861 and why isn't he considered Spanish if the area he was born in was under Spanish rule?

Cristopher Columbus was born in the Republic of Genoa, on the Liguria region of the Italian Peninsula. Although the concept of an Italian identity and language is complicated, the concept Italy never disappeared as a geographic construct. I wrote a rather long-winded answer about the meaning of the word Italy here and a more compact answer on Columbus' early life here. Although I'm more than happy to clarify anything you might be confused about.