Im not american, but I am pretty sure any attack on america itself would fail. An economic/trade war would do much more damage, since they arent self sustained. Then theres dissenters, and migrants from other countries living there. Simply putting it as a war just isnt feasible. And if they just decided to nuke everyone, im sure everyone would die due to mutually assured destruction. So yeah this guys a dumbass, but maybe in his mind its like a video game, they do have the most advanced military, in more ways than one, and their navy is the second largest airforce, second to their airforce. Im sure they can defend themselves easily. At least till resources ran scarce.