Regardless of your position on World War II, the atomic bombings of the civilian populations in Hiroshima and Nagasaki is morally reprehensible. Many have expressed regrets and offered apologies.
President Obama attempted to apologize in 2010, but was rebuffed. That does not mean that we should give up. We need to try again and demonstrate to the world our sincerity never again to repeat those mistakes and our commitment to world peace.
There should be an official apology from the President of the United States, even if Japan is unwilling to accept it.