2042 people died in the attack.  Only 57 were civilians.  The rest were military.
The nuclear bombing of Hiroshima and Nagasaki killed 150,000 to 250,000 people, and nearly all were civilians.
The unprovoked US attack and occupation of Iraq killed hundreds of thousands of innocent civilians (possibly more than a million) and turned millions more civilians into refugees.  If Americans were concerned about about killing innocent civilians, then they'd probably have at least a good idea of how many Iraqi civilians have died as a result of their actions in Iraq.  Certainly the American news never talks about the total number of civilian deaths in Iraq.  IMO, the American public doesn't care about innocent civilian deaths, unless their idiot box tells them its important.
Americans were no more concerned about innocent Chinese deaths back in the 1930's than they are concerned now about innocent Iraqi deaths, or innocent Vietnamese/Cambodian deaths during the Vietnam war.  US propaganda at the time mostly ignored Japanese atrocities.  In the early 1930's the US was somewhat pro-Japan and anti-China.  Japan was a US Allie during WW I.  The US tried to maintain good relations with Japan and ignoring Japan's post WW I atrocities helped smooth trade relations.  But as Japanese atrocities grew ever more outrageous they eventually became too big to ignore.  The 1937 Rape of Nanking did make the US news and Roosevelt condemned it.  But he also ordered the withdrawal of American troops from most of China, leaving the Chinese to fend for themselves.  While the Japanese raped and slaughtered innocent Chinese civilians, the US continued to sell war materials to Japan.  If the Rape of Nanking outraged the US, then why did they continue trading with Japan for another two years????
BTW, I agree with the US embargo against Japan...  I just said that once the US cut off Japan from oil, war was the most likely consequence.  The Pearl Harbor attack was successful as a result of careful Japanese preparation and American incompetence.  After Pearl Harbor the US military has tried to maintain a constant level preparedness for another Pearl Harbor like attack.
The US, UK and France bombed Iraq daily-weekly after the ceasefire agreement 1991.  It just didn't make our news very often.  Once in a while Iraq would defend themselves from American ceasefire violations and our propaganda would portray their defense of their sovereign territory from hostile attacks inside Iraq as offensive. The propaganda was so twisted, most Americans still believe US bombing missions inside Iraq were defensive. (no-fly zones and other related BS)
BTW, I agree with what the US did in the northern Iraq.  US ceasefire violations probably averted a bloodbath in Northern Iraq, so I'm not criticizing the action, just the propaganda which lied about it
Technically, when a US military aircraft flies into Iraqi airspace and bombs Iraqi military sites, the US is attacking Iraq.  Claims that Iraq was attacking the US  would be similar to claiming that someone attacked me, by using their face to hit my fist.  American propaganda also created a perception that these American attacks against the Iraqi military were backed by a UN Resolution, but they weren't.  The same propaganda also created a perception that Iraq still possessed WMD stockpiles, even though UN weapon inspectors were more or less certain that Iraq no longer possessed WMDs back in 1998 before Operation Desert Fox.
Iraqi Sanctions: Myth and Fact
Anyone actually read the weapon inspector reports, would have known that US claims about Iraqi WMD stockpiles was 100% BS.  That was known in 1998 and in March 2003 just a couple of weeks before the US led invasion:
Security Council 7 March 2003
Our news never reported anything which did not support the case for war.
Regarding nuking Hiroshima and Nagasaki...  I don't believe President Truman, his cabinet or the generals understood the destructive power of nuclear weapons.   They were given numbers, but in people's minds, the numbers didn't translate to leveling an entire city and killing hundreds of thousands of people.  If Truman understood how destructive the bomb was, he may not have used it on cities, but demonstrated it to the Japanese as many scientists working on the Manhattan project recommended: 
"The Scientists' Petition:" A Forgotten Wartime Protest