The Japanese did not surrender until after the nuclear weapons were used.
There was no "ignoring a surrender"----they had every intention of fighting on,street by street .
They tried to negotiate a surrender with better terms through the USSR, those attempts were ignored by the Allies.
^This.
And the dropping of the bombs on Hiroshima and Nagasaki was as much about sending a message to the USSR as it was about forcing an end to the war. The US leadership assumed that it would hold a nuclear monopoly for many years to come, and could use it to keep the "red menace" at bay. Little did they know about Claus Fuchs and other soviet spies within the Manhattan Project who gave the USSR enough data to be able to build a bomb by 1949.
Most historians point out that the approaches through the USSR were not a Surrender,but an offer of a negotiated Peace,with Japan retaining much of its Pre-War possessions,(like Manchuria) its military forces & material.
This was not acceptable to the Allies,who didn't want to have to fight the War all over again if the Japanese reneged on the agreement.
They had seen that happen with Germany in Europe,where the Versaiiles agreement was slowly frittered away,& what the Japanese wanted were much more generous terms than the Kaiser's Germany ever got.
Even so,the approach was tentative & informal,as the hardliners in Japan were quite capable of assassinating anyone thought to be Defeatist!
People who only know the USA as the sole "Superpower" don't quite understand the times.
At the beginning of WW2,the USA was only one of a number of "Great Powers",& even by its end,was not in the pre-eminent position that it later attained.
If Japan had managed to effectively "Neutralise" Australia,the USA would have had a difficult job,with only small island bases to work from.
As it happened,Japan was the side in that position,but even,so,the "Pacific War" was a close-run thing.
The USSR entered the War against Japan late,but they did defeat, & capture many of, a large Japanese force in Manchuria,making Japan's continued claims to that territory academic.
Of course,it wasn't PC in the '50s to credit the USSR with anything,so that bit got left out of the history books.