Consider the sentence
What is the 27th state of the United States?
The answer is Florida. Yes, Florida is a place. But Florida is much more than a place. A State in the USA is a semiautonomous political unit. It has the power to form a government, tax its residents, formulate educational policies for its residents, say that it's compulsory for its residents to wear seat belts, draw up laws about self defense, and so forth.
In what is now Florida, 'Florida' is being thought of or conceptualized primarily as a State. Thus, native speakers use what here, and native speakers do not use where in a phrase such as '*where is now Florida'.