Just so you know Russia would support China, and they have tons of nukes left over from the Soviet Union
@genocide, you could have fooled me, China and the us' economies are so different they're variably incomparable, China's is NOT in decline, it's growth has slowed down, that's perfectly reasonable. 7:1 gun ratio? You're trying to tell me there is (in civilian hands right now) 2.232 billion guns in the USA? For someone who supposedly is involved in economics, your maths skills are worrying.
Sorry, also mr economics, us spending 2014 = the combined spending of ranks 2-10 and half of 11 (list by military spending). That's a whole long way away from the "top 20" closest.
Military spending also doesn't necessarily mean much. There have been many, many, many times that a country who spends a lot less on their military have won.