What if a Hacker just Uploaded a video saying "hello America what a good day to be alive right? what about a little nuclear detonation to even make it better!"

If a mysterious hacker uploaded a video with this message, law enforcement would immediately take action to try to identify and apprehend the hacker. The FBI and other government agencies would also investigate the incident to find out who was responsible, and also to learn more about any potential connections between the hacker and the nuclear detonation. The consequences of this type of incident would be grave, including severe sanctions against those responsible, as well as national security threats in the future.