Most of the civil government was unaware of the actual nature of the special weapons in China. This was partly willful ignorance as well as partly due to the fact that most Japanese military units were more or less independent of the civil government.

In any case, the use of any of these weapons against the United States never occured, especially "retribution" for Hiroshima. The closest the Japanese got was the attempted raid on the Panama Canal by some of the I-400 submarine carriers which were to detach Seiran floatplanes to attempt to damage the canal. This was later changed to be an attack on US carriers at Ulithi Atoll, but the war ended and so the entire operation was cancelled. There was also considered deployment of biological weapons on Saipan and the Mariana Islands but it never actually happened.

Now, there was also allegedly a plan to use these same I-400 submarine carriers to launch an attack on San Diego. However, I have doubts as to the historicity of this event, both because its supposed codename "Sakura Blossoms at Night" and supposed implementation (balloon bomb or kamikaze attempt with plague infected fleas) seems to be a combination of stereotypical tropes about Japanese military operations. Japanese operations never had complicated names like the one above-in fact, the one "Operation Cherry Blossom" was an Allied attack on Bougainville. In addition, the sheer likelihood of a Seiran getting into a San Diego with heavy defenses and a combat air patrol was extremely unlikely. Lastly, and this is probably the most important, any kamikaze crash by a plane would cause a fire or enough direct impact to kill the plague-infested fleas, rendering them unable to infect. The Japanese command, while certainly stupid and incompetent, were not ignorant.