Maybe you are thinking about the 58 megaton bomb that was detonated on October 30 1961 over Novaya Zemlya? ==
Yeah this one the "country buster". But accually thier yeild was artificially decreased twice for test. Its full yield is 100M+. This bomb was produced 40+ years ago probably quite few devices. Such bomb make whole NATO rudiciluous isn't it right?
No, this type (and other big) bombs are useless, that is why they are not produced anymore.