Were the Americans justified in dropping the atomic bombs?

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On the 6th August 1945 a US B-29 bomber dropped an atomic bomb on the Japanese city of Hiroshima, instantly killing around 80'000 people. As the bomb dropped, a lightening flash burst across the sky. In seconds, a giant mushroom cloud of poisonous gases and smoke covered the city. It estimated that more than 75'000 people were killed instantly. Thousands more died from burns and radiation poisoning in the hours, days and weeks followed. When Japan still refused to surrender the US dropped a second bomb on Negasaki three days later. Another 40'000 people died instantly. On 15th August 194, Japan surrendered unconditionally. The effects of the atomic bombs, however, would last for years as over the next decade half a million people died from radiation poisoning. In my opinion I don't think that the Americans were justified in using the atomic bombs because, most of the casualties were effected by the bomb were innocent people caught in a global battle for power and supremacy. This shows that Americans were just looking for power and weren't understanding how it would effect innocent people because because they just wanted to get Japan back for bombing Pearl Harbour.