Because Hispanic is considered a culture and not a race. There are blacks, whites and people of Asian and indigenous American (and by American I mean North, Central and South) descent who were born and raised in the Spanish-speaking cultures of the Americas, which (most of ) the US and Canada are not.
Peru, for instance, had President Fujimori (before he was busted for corruption), whose distant ancestors were from Japan, but he was Peruvian-born and raised. So in that sense, he’s Hispanic.