Top 10 Countries with the Most Spanish Speakers

Well yes, there are people in Spain who have a different mother language than Castilian Spanish, but they should count in these numbers because everyone in Spain speaks Castilian Spanish as well.

I'm assuming you mean southern Florida. I haven't been there but I've heard that Southern Florida is very diverse with many people from all over but Spanish speaking people make up the main groups (Cubans, Dominicans, Puerto Ricans, Colombians, Venezuelans) whereas in Northern Florida it's mainly English speaking Southerners. I've heard North Florida being called South Georgia because of how much more like Georgia it is compared to southern Florida.

No, everyone in Spain speaks Spanish natively, there are bilingual regions, but everyone speaks Spanish.

It is the native/mother tongue of most people in those regions though. People can have more than one native tongue, people in Catalonia, Valencia, Galicia and the Basque Country all speak Spanish natively, regardless of whether they also have another native tongue. No one considers them foreign speakers of Spanish.

Almost everyone who speaks Spanish in Spain does so natively... People can have more than one native tongue, why is that such a difficult concept to understand? Would you consider Hispanics who grow up in the US, and thus speak Spanish natively at home but do their entire education and social life in English, as foreign speakers of either of those languages? No, and it's the same in Spain, the only potential exception being older people in secluded villages that never mastered Spanish in school and never used it in their daily lives, but that is a minuscule minority. Pretending like the entire population of like 5 different regions are non native Spanish speakers is ridiculous