man, peope REALLY REALLY seem to forget and/or ignore how powerful the US armed forces really are.
Yes China has 10x the man-power, but this is 2012. There isn't a single country that can even remotely compete with the US armed forces due to its sheer technological advancements over the rest of the world.
To put this into perspective, the USA had Nukes in the 1940's. China did'nt develop nukes until 1964.
if a war between China and the US did break out...
1.) It would turn into the next World War.
2.) it would be devestating
3.) it would be remarkably difficult for invaders the invade the USA. (It would HAVE to be done via the AIR as the American coastlines (even outside the USA) are to well protected. china would have to launch every ship in its fleet to the coast of a south American country without the US discovering them (by shooting out all allied controlled satellites), march/fly a thousand+ miles to the USA border while fighting other nations for a naval invasion to work. And that would leave China's mainland completely defenseless.
That's not even taking into account the hate the governments of other powerful ally countries have for communist China. Its logistically impossible for China to win a major war against a major power. Particularly the USA.
...uhh...ill just put my favorite quote of all time here.
"Welcome to Pain, the second of three...You have dealt the first...now deal with me!!"
