How are Latin Americans not considered white, when Spaniards are considered white?

Latin Americans are fully blooded spaniards living in South America. The only Latin Americans who are not fully blooded Spanish, are Afro-Latins or Indigenous people. Surely, not every Spanish sailor mated with an Indigenous of South America creating the Millions of supposdely non-white Spaniards of South America today? Even Sicilians of Italy are darker than most Latin Americans.