I think you're combining three questions.
1. Can you learn to speak fluently without speaking?
The answer to this is obviously NO. You need to practice what you want to do. You can learn to read fluently without being able to speak very well (I've taught courses doing that), although you need to learn some sort of subvocalisation. But obviously there are fluent readers of dead languages like Ancient Egyptian who don't speak them.
2. Can you learn to speak fluently without visiting the country where that language is spoken?
The answer to this is obviously YES. Champollion (the man who deciphered the Rosetta Stone) could famously speak Arabic fluently enough to confuse native speakers without ever visiting Egypt. And this was before audio recordings were available. But he kept diaries in the language and practiced all the time (I assume with native speakers but I don't know if that was the case).
3. Can you improve your spoken language by reading?
The answer to that is also YES. Reading will expand your vocabulary and your grasp of the idioms and underlying constructions of the language. Ideally, you will want to combine this with speaking practice so that you can translate this knowledge into conversation. Reading will also give you cultural background to the language that simple exposure to it by living in the country will not. Imagine how much you have missed by not growing up in the country. Books will contain so much of that background knowledge. But so will films and TV shows, so I'd recommend a combination of both.
It is also important to note that living in a country where a language is spoken does not guarantee that you will learn to speak it at all, let alone with any degree of fluency.
Other things to remember are that there are many languages (most languages in fact) that are only spoken by relatively small communities within larger countries so living among them is not as visiting a country and takes a lot more effort to make happen.
Finally, fluency and language competence in general are fluid concepts without clear boundaries, although there are certain folk pre-conceptions.