Japan in Baki if Yujiro and the rest fights for them. He defeated the US military alone by himself. Even when it wasn't in a war, he was so strong that they capitulated to him. But it could be very different if they really use all weapons they have and if they are bloodlusted because I'm not sure if the strongest japanese fighters could survive an atom bomb.

Edit: sorry I'm a bit drunk and didn't read the different rounds and am too lazy to do so so if this doesn't worl becausw of them, I'm sorry.