This week marks the 70th anniversary of the atomic bombing of Hiroshima and Nagasaki that took place on August 6th and 9th, 1945 respectively.
The Nagasaki Archive that we have referred you to in the past still works but relies on the Google Earth plugin, so you may have difficulty accessing it. You can, however, access the individual KML files here and load them directly in Google Earth without the plugin. For some files there are both Japanese and English versions. Possibly the most interesting file is this one, which has a number of photos correctly positioned.
The Nagasaki Archive files can be opened directly in Google Earth if you do not have a browser that is compatible with the Google Earth plugin.
We tried to find other KML files related to the bombing in order to explore the sites in Google Earth but were not very successful. Google Earth Hacks features a few related files but they are not very detailed and one of them links to photos that are no longer available. The best is this one that has a number of relevant locations in Hiroshima and a working overlay showing the damage to Hiroshima castle.
One of the key sites, which is close to Hiroshima Ground Zero, is the Hiroshima Peace Memorial, which has had Street View since 2011.