I don't think that dopey NYC video really conveys "whatever", more like we don't know what the fuck we're doing

What would you advise, instead?

If a nuke goes off, the FEMA steps of get inside, stay inside, and stay tuned is your best bet.

Yes, some people will need to evacuate, but it's a pretty small slice of the overall affected population-- better for everyone to wait for specific instructions on what to do than to have everyone in a massive jam trying to flee and exposing themselves to high levels of radiation and other hazards.

I'd be afraid in an atmosphere like NYC that the damage to buildings, gas pipes, electrical wires and the like would make staying in whatever building you happened to be in quite dangerous in its own right.

I guess it's still probably less dangerous than risking radiation exposure, but it seems like an overly broad solution.

The FEMA advice goes into this in detail.

Basically, it all depends upon yield and altitude, but there's often a pretty large zone with moderate to minimal damage but with significant outside radiation hazard for several hours

A lot of those hazards, too, like downed wires-- are worse when you're outside. Basically, absent fire or imminent structural collapse, you should stay in place after a nuke and await some kind of orderly, systemic assessment of what's going on.

I don't think you need to worry about duck and cover if your city gets hit by a 50Mt warhead.

If you find yourself alive and able to chill in basement for a few days, that’s the best advice.