I wanna start to write my first book. My problem is if I could use real country names in my book. For example, can I say that the action takes place in USA, California, Los Angeles or in China or in Iraq? What if my book is a fiction and I transform the story into a conspiracy theory like saying that UK is trying to destory the world making a secret pact with Russia to land some nuclear bombs on the center of Europe. And what about using real-world problems in my book? For example; the refugees crysis, the earthquake in Japan or any other things like these?
Publishers will include those disclaimers of liability in the frontpapers. As long as your book is marketed as fiction, you don't have to worry about legal ramifications for including the names of real-world countries.
Now, for including humanitarian incidents or disasters, you'll want to examine how you're including them and why. One-off references can contribute to setting, by rooting your novel in a particular time and place.
But if (for instance) the refugee crisis in a certain country makes up a significant portion of your book's plot or setting, you'll want to do the research that will let you examine it in a thoughtful and empathetic manner. Otherwise you run the risk of appropriating a serious event instead of reflecting on it.
If you are writing a work of fiction, you can write what you want.
Country names are not copyrighted features of someone else’s work. You can set your work wherever you want to. A caveat is that if you set all or part of your work in China and you don’t know anything about China, it will be unrealistic and the reader may lose their suspension of disbelief. The adage to “write what you know” definitely applies here.
You can make up worldwide events wholesale. Consider that the entire world blows up in many books and movies. Aliens land. Plagues wipe out all but a handful of survivors. Go for it.
You can certainly be informed by actual events. But again, if you don’t “write what you know” then you risk being unrealistic and taking the reader out of the story. It might be better to create a fictional event that is informed by real life rather than describe actual events in an uninformed way.
But there is nothing stopping you from writing what you want to write. You don’t have to ask anyone’s permission.