Mourning, sayinng sorry, moment of silence......those things are free.......and buy more good will then any aid or any other peace mission would.
I think world is pretty clear on what happens when you awake the gentle giant, so they won’t be confusing this presence as US going soft.
So in my view, this is pretty harmless. 99% of the people outside Japan won’t even hear about it.
along the lines of “very sorry your miliarist government
made this unfortunate bombing necessary”...