What does Chief Bromden's reaction to seeing the outside world indicate?

The Chief realizes that the outside world has changed and that, in fact, he has changed as he sees things through different eyes. In reality, he now has more strength to face the outside world. One thing, for example that he is amazed at is the way farming has changed. The fact that he "breaks out" at the end shows that he is not suited for confinement in the asylum any more compared to how he was when the novel started.