To make maximum effect of a nuclear torpedo from Russia

Likely it would go off 20 miles or so off the Atlantic coast. Wherever this happened the 300 foot tidal wave likely would go all the way to the Appalachian Mountains and up into them over 1000 feet or more before the 300 foot wave stopped. Many people don't realize just nuking a city isn't the best way to kill everyone for hundreds of miles. A nuclear torpedo set off way out to sea would be the way to kill the most people in any nation with a seaboard. So, likely there would be no warning at all when this happened and no time at all to prepare or escape. This is also something North Korea is prepared to do too with it's submarines along the Pacific Coast of the U.S. And then the next moment North Korea would be a crater. And the same with Moscow or more if Russia did this within an hour of this happening.

Our military is set up  on the "Better dead than red motto" still which means basically "The U.S. is prepared to end the planet earth and all life upon it rather than to lose any war. It has been this way since World War II and why so many nations are afraid of the U.S. but also respect us because of this stance. I think Hiroshima and Nagasaki which saved 900,000 to 1,000,000 American lives set the stage for this attitude which continues in our military today.