TNT explosions look very similar.

Ask yourself... Why did they provide the footage? Simply to promote fear in our enemies? Why have there been no modern film releases of the devices since? Was it all just propaganda?

To be clear on my position, I'm actually in dissent with OP and DecodingSymbols on the existence of nuclear devices.

I believe they do exist, but none have been used militarily. I think the efficacy of a chain reaction is far too uncontrolled outside of a nuclear reactor, and the reliability of such a device scales so wildly as to be unusable outside of a dirty-bomb scenario.

I believe in the Firmament, which means all things have a triune realization. Exoteric (Actual Nukes and Nuclear Fission/Fusion exists), Esoteric (Comms for Explosive Blackmail that can level a Nation, AKA "Q-Level-Clearance"), and Spiritual (Global FEAR of Mutually Assured Destruction)