Just for you: http://nuclearsecrecy.com/nukemap/ Pick a typical warhead of 750kt and detonation in the air for maximum effect. I picked Chicago, where I live. The air blast radius (ruined buildings) is almost 4 miles. That means diameter is 8 miles. I look at air blast because thermal radiation and other effects are survivable and won’t immediately kill you. Considering that in North America we will have a 30 minute warning, it’s reasonable to assume most people will run inside nearby buildings. So, 8 mile diameter seems like a lot for Chicago, right? Not really: Chicago + suburbs Covers over 10,800 square miles. So, to effectively exterminate everyone in this metropolitan area the attacking nation would neeed to spend around 1,000 warheads. Russia has only 2,800 that are ready to go. Can Russian attack cause massive damage? Of course! Will it spell the end of this country? No!