I’m not making anything up; they did react, and did decide. After, as you say, a “bomb that wipes out a city in millisecond”, the war council met and resolved to keep going. It’s not as if the bombing destroyed crucial lines of communication; it’s not that key government officials had a hard time reaching the capital to form a quorum, or that assorted decision-makers then refused to make up their minds. It’s that they reacted and decided rather like American decision-makers did after the attack on Pearl Harbor: let there be war.
Heck, let’s run with that parallel for a moment. Japan bombs Pearl Harbor, whereupon America promptly reacts and decides to fight back; it doesn’t take three days or two days, since it doesn’t even take one day for FDR to go before Congress and make the Date Which Will Live In Infamy speech; Congress, of course, promptly agrees to declare war. So now imagine that, some three days later, Japan bombs us a second time – whereupon America rethinks everything and says, whoa, hey, our mistake, we surrender, name your terms.
In that bizarre counterfactual, I’d have to say the first attack wasn’t impressive enough to make us surrender, sure as the second was enough. And I don’t see how the attack on Hiroshima fails to duplicate the attack on Pearl Harbor; Japan’s decision-makers don’t see anything worth surrendering over, just like we didn’t, and so opted to fight back just like we did. And so we hit them a second time, whereupon they took a vote and –
–well, even after Nagasaki the ministers deadlocked instead of lining up a slim majority either way. But (a) at least that’s progress, and (b) it set the stage for Hirohito to then step in and break the tie, which hadn’t been the case after Hiroshima.
The folks who were refusing to surrender after Hiroshima don’t seem to have been any more or less ‘in shock’ or ‘horrified’ than their counterparts who were arguing in favor of doing so; they all reacted and decided – with no indication that any of 'em were more ‘shocked’ or ‘horrified’ than America’s decision-makers had been on December 7th, and 8th, and 9th.