Actually the Kamikaze were extremely effective. The upper brass were intensely worried. The Fleet would have had to be within very easy range of Kamikaze attackers when Japan was invaded. Japan was trading a dozen aircraft and pilots for a United States Navy warship. Unsymmetrical warfare with a vengeance.
Nuclear weapons turned the tide.
No. Check out VD Hanson's chapter on this in his book, "Ripples of Battle." They were only "successful" in that they do exactly what suicide bombers always do: they removed the self-imposed restraints of a humane power and caused us to say, "OK, you want death and destruction, here it is."
You act like the bomb was something special. If we hadn't had the a-bomb, and still had to invade Japan, you would have seen marked changes in tactics after Okinawa and a conventional bombing campaign that would have made the Tokyo fire-bombing look like a Cub Scout campfire.