The Chinese Economy is currently based on the health of the US, if the US were to hit a complete financial crisis, China would as well, furthermore, China's economy passing the US after 2030 is based on their economies GDP having a growth of 10% per year while the US has little to no growth, accounting for no variables. China's got problems ahead of them, I would see India becoming more of a power in the very long term, for the short, it's safe to say the US will continue to be the most powerful, and influential, international language of business is English last time I checked, and there's a reason for it.

1) Troop numbers don't count for much when you can't properly arm them

2) How can the US get overwhelmed when it has complete air and navel superiority? The entire war would be fought in China

3) Comes down to production, purchasing power and technology 3/3 for the US (furthermore the US has a stronger army,navy and air force then China, do some research anywhere as I don't feel like making this 1000 words)

4) India could not take China as numbers aren't all that count, China is technologically superior to India and therefore would win a 1v1 war

5) People who could beat China in a war: USA, EU and Russia

Excellent points, but you don't need docks when your carriers run on nuclear power - means you never refuel :)

And the US has had more missile systems more complex since the cold war, therefore we can reduce both navies to 0 in the fight making air force the main way of delivering soldiers and adding (in your scenario) a weight of 2 to the air force, where the US reigns supreme. So either way you compare the militaries, it is 3 out of 3 for the US of A. But in production (as proved and tested the US has the upper hand allowing it to produce more navel ships more quickly then any other country in the world, again 3/3)

Ok so it is estimated that China spends 70 Billion on Military

The USA spends 700 Billion on Military, 1.35 Trillion in the Department of National Defense (which is more then Chinas entire GDP), so personally, they could be 500 billion off and the US would still spend more then China could produce ... this isn't a good question, it should be is there any 2 countries that can defeat the US in a war ... answer probably not unless you count the EU as one country ;)