The United States May have retaliated against Tsar Bomba, had it been detonated in the United States. Although it was meant to be a threat to the United States and anyone else who dared to mess with Russia during the Cold War, the bomb was never used against any enemies of Russia.
The Russians tested the Tsar Bomba near the Artic circle. As far as we know, there were no casualties and no buildings were destroyed during the test. We will probably never know the true consequences of detonating such a massive bomb.