Please explain the effectiveness of the narrative point of view in Alexie`s story "This Is What it Means To Say Phoenix, Arizona".
First, let me say that I'm not sure what you mean when you use the term "effectiveness." By "narrative point of view" I'm making the assumption that you mean Alexie's use of a third person narrator who doesn't always seem to be omniscient throughout the book Lone Ranger & Tonto Fistfight in Heaven, but seems to be fairly clear in the story "This Is What It Means..."
If you are asking whether the use of a first-person narrative point of view would be more effective than the limited third person perspective of Victor, it is really just a matter of opinion. I think that Alexie's third person perspective of an unreliable narrator like Victor is a highly effective way to convey the emotional impact of his father's death and the memories of his childhood it triggers for him as well as his sense of loss in general, not just for his father but for the Native American way of life.
If Alexie had used a first-person perspective, then the reader would not understand Victor's plight as well, because Victor himself does not really understand his emotions. He uses Thomas as a touchstone for how he is feeling, and he doesn't even realize it. And even when the perspective switches to Thomas, it is Victor's memories of Thomas that the reader is getting, giving the reader a greater understanding of what it means to be Victor Joseph.