Time frame-late 1970s. This was a made-for-TV movie about a terrorist plot to detonate a nuclear weapon in New York.

It was kind of a combination of "War of the Worlds" and "24", since it was done in the form of "news reports" as the terror threat evolved, supposedly in real-time. The terrorist make demands, and have a deadline (within the running time of the show) for setting off the nuke.

In the end, the bomb was located in a small boat in New York harbor; an assault was staged by a US Army Special Forces team, and the terrorists were killed in a very realistic shootout. A special bomb team is called in and tries to deactivate the bomb in the moments before the deadline runs out...but they don't make it. The movie ends when one of the EOD guys goes "oh my God!", then the screen goes white, and one of the stunned on-air news people just looks at the camera in disbelief, totally stunned.

Anyone remember this movie?

Special Bulletin.  Aired 1983.

Definitely the above.

You might also be interested in Countdown to Looking Glass, which takes a similar "news report" perspective on a looming nuclear exchange.  Without Warning also bears mention.

The original war of the worlds radio broadcast, incidentally, is still great listening.  You can find it from a google search.

I remember my Aunt walking in on the middle of it and nearly screaming "What the hell have those damned scientists done now?!?!"  

13 minutes, 44 seconds.

Slacker.

Hey, the "Obscure Nuclear Fact Wanted" signal woke me up from a sound sleep––I got here as soon as I could!  

I laughed at the end, where the "bomb squad" was trying to disarm the nuke and they had ten seconds left and one of the guys panics and tries to run away.

On another note, there was a book in the early 1990s called "Alternities" about some guys who find a gateway to alternative universes (256 of them, I think).

In one of them, college students plant a bomb on the same ship (Lexington ?) that they did in this movie.  The explosion caused that version of America to become more right-wing, to the point where Americans began to turn in suspected enemy agents and other criminals.