It's sobering to think that even a small conflict could escalate given the right participants. While there is no doubt that the size and strength of these weapons have grown exponentially we an only hope that technology and counter weapons exist such that if there was ever such weapons released upon our nation that we could counter them or intercept them and destroy them before they could go off. Otherwise we have to rely upon calmer heads to prevail.
Here is an interesting site to determine just how much damage could be done if such weapons were released. If the largest Russian weapon was dropped on the center of Huntsville then the fireball and 3rd degree burn injuries would extend all the way to Rogersville. That is scary. To think that our whole world and life could be altered in a second or within any 30 minute period. In any 30 minute period we all could be back to the stone age and very ill prepared to survive given what would be left.
http://nuclearsecrecy.com/nukemap/
If you choose to try it then under #2 Yield, just choose a preset from the dropdown menu and let the other defaults be what they are but we all know that no nation would just send or drop one.