All of the footage you can find of aboveground tests is from before the signing of the Limited Nuclear Test Ban Treaty in 1963, which was an agreement to, in part, not detonate nuclear devices anymore in the air, water, or in space.

Although non-signatories continued atmospheric testing until 1980 when the PRC conducted their last atmospheric test, I'm not aware of there being any footage available to the public of that test. The final US atmospheric test was codenamed Tightrope, was conducted in November 1962 and it can be viewed among several other tests in [this video] (https://youtu.be/fFYmcwNr_hs).