Will the entire application be re-rendered if some internal (somewhere in the application) state of one of the components changes?

Question

JavaScript

Let's say we have an application.
Here is such a structure

<App>
  <Header/>
  <Footer/>
<App/>

The header and footer have their own state.
If somewhere in the footer there is a button that updates the state of the footer, will the entire App. or only Footer which has its own state?

Answer 1

Of course not. Only "that part" (that component) is rendered (redrawn) in which the props/state were changed + all children if they do not have optimizations (for example, they can be made as stateless, pureComponent or have shouldComponentUpdate - then they will not be redrawn with the described conditions).
I see the question has been updated: yes, only the footer.