[Crono]

Sorry for the double post, but let's see:
China - large numbers, but they're really weaker than you think. Besides, once their government falls it'll all be gone.
Russia - LOL. No comment.
India - Meh, they're not bad. Worse than China, but still good. Not many technological advancements here. They have nukes however.
Britain - They're small. Not as big and as advanced as the US.

The U.S. is the super power. The technology it's army has is well beyond any other army in the world.