I suppose Americans will always feel Japan deserved having two A-bombs dropped on it for the massacre at Pearl Harbor. At least that is what Donald Trump is suggesting. If it is any consolation to the Donald, the current Japanese PM offered deep repentance for Japan's actions during WWII, but for many Japan will never be sorry enough.
We had a long ugly war with Japan that saw many dead, but couldn't possibly compare to what China suffered during WWII. China lost an estimated 14 million people. Still, none of this justified dropping atomic bombs on Japan, especially with Japan on the edge of surrender. The only thing left to discuss were the terms, which was going on at the time. It seems Truman wanted to speed up the process before the Soviet Union tried to make more territorial claims to the region. Plus, try out his new toys.
One can argue that Japan hasn't been overly contrite over the years. MacArthur was never able to wrangle an apology out of Hirohito, although the emperor purportedly warned that bombing Pearl Harbor would be self-destructive. Nevertheless, the empire was abolished and a new parliamentary form of government put in place, which helped speed Japan's post-war recovery and has remained very resilient. Japan is now counted as one of our closest allies.
Obama going to Hiroshima was meant to put the matter to rest once and for all. But, Trump and other Republicans work from the old Southern adage, Never Forget, preferring to keep Japan at arm's length. Funny for a man who prides himself so much on his great negotiating skills with Asians. He probably thinks Japan has gotten the better of the deal since WWII, and that Obama's visit represents the end of his "apology tour," as Charles Krauthammer put it.
In his speech, Obama no more apologized for the events of WWII than did Shinzo Abe. He offered his regrets and urged listeners to push for a world without nuclear weapons, referring to it as a "moral revolution,." This is ever more important with world leaders and would-be leaders both playing the "nuclear card."
Nuclear disarmament is something sane persons can agree on. The US has in place non-proliferation treaties with Japan and other countries to avoid any further escalation of arms in the Pacific Rim. However, the US and Russia have to greatly reduce their massive arsenals if they expect other countries to honor these agreements. There are the many open nuclear weapons programs like that in India and Pakistan, and "secret programs" like that in Israel. It is little wonder Iran wanted to join the club.
Obama has waited a little too long to launch this "moral revolution." It would have been better to have made it the cornerstone of his foreign policy and begun de-escalation when he first came into office. We have had so many missed opportunities in this regard, the most infamous one being the Reykjavik Summit when Gorbacev was apparently willing to negotiate a full nuclear disarmament agreement if the Reagan administration was willing to give up its strategic defense initiative, aka "Star Wars," but sadly there was no deal.
Nevertheless, it was important to have a US President visit Hiroshima and recognize the horror that took place over 70 years ago.