1) The SU already knew about the atomic bombs even before the USA used them as during one of the congresses that was held between the allied forces while WW II was still going the American president said to Stalin out of the blue they had the atomic bomb to see how he would react. Considering he wasn't phased, it seemed he already knew.
2) The SU was able to build their own atomic bombs a few years after the war due to scientific research they were able to obtain from Germany, who likewise were building it. They didn't copy the Americans, they made it themselves.
3) People who complain about the USA having used the atomic bombs, seem to have no idea about how the war was actually going. Just conquering a series of small Japanese islands were aready taking a huge amount of lives and materials. The Japanese were also not your average enemy. To win a war or you destroy your enemy completely or you make him surrender. The Japanese were so strongly indoctrinated that they would have never surrendered. They had been building an entire arsenal of kamikaze weapons not only for their solders, but for the regular civilians. They made airplanes, submarines and other weapons specifically for suicide missions and they been preparing to use them on a massive scale on the moment the USA would try to take the mainland of Japan. Among others they created literally a flying bomb, a bomb with wings, a cockpit for one person and a booster jet that was attached to a plane. The bomb was dropped from the plane and then the pilot inside the bomb had to maneuver almost in a straight line to the intended target while going around 200-300 km/hour with a bomb strong enough to sink a battleship in one hit. For the record even Hitler thought this was going way too far.
Conquering Japan in those conditions would have taking a hellish long amount of time, it would have taken a huge amount of money and the amount of American soldiers that would have died could have ended up in the 100 000 or even in the millions and then I'm not even talking about the Japanese losses and this on a moment Germany already had surrendered. This is a scenario no one wanted, so they decided to show a display of power. In three days Japan surrendered. People who say that the atomic bomb shouldn't have been used, seems to not be aware that the only alternatives were far worse as the Japanese showed no intention whatsoever to yield.
4) You seem to be not aware of the nature of the atomic bomb. It draws most of its use as a scare tactic. Turning it into a hidden, secret weapon, would have rendered it nearly useless. By showing the world the atomic bomb and that it clearly works, makes everyone think twice before going to a war. Using it as a secret weapon when a war is already underway, is way too late. The USA used the atomic bomb on what probably was the only time and place since its creation it was justified to be used. Using it as a secret weapon would have been the worst idea ever as that wouldn't have just lead to WW III, that would have lead to the Apocalypse as unlike you claim, it could not defeat a nation. That became very obvious when they had to drop two of them before Japan capitulated. What do you think would have happened if they dropped it on the SU who also had those bombs? The SU would have returned the favor and that's already being very positive as thinking that somehow American airplanes would have succeeded in getting so deep into Sovjet territory, is very unlikely.
