I think a lot about the China vs America issue, and I have some interesting thoughts.
For starters, I highly doubt either country could invade the other. The Pacific Ocean is vast, and the US has a pretty good number of Pacific bases. This, combined with the high effectiveness and superiority of the US Navy (especially when considering naval aviation and submarines), would ensure that any China invasion fleet would be destroyed before if got close to American shores.
In addition, you have to consider the enormous potential for a highly effective citizen resistance in both countries. The US civilian resistance would be quite strong due to the number of combat veterans and personal firearms. The Chinese civilian resistance would be quite strong, because high numbers of high-school graduates in China receive rudimentary military training, and I have to assume that the government has hidden stockpiles of basic light infantry weapons (light mortars, assault rifles, RPGs, and light machine guns).
But to answer the original question, a website I have found (and I do realize that random websites are always a dubious source), www.globalfirepower.com has it listed as:
- America
- Russia
- China
- India
- UK
The website claims that it evaluates 45 different factors, including size of nation, size of armed forces, number of planes, ships, tanks, etc, so take it for what it is.