I don't think China is a scared of the US as you think. They could crash our economy and throw us into turmoil in a second. Then, if military action is involved, they have so much established manufacturing and natural resources, they could ramp up like we did in WWII but faster and better. Not to mention, with Russia and N Korea just around the corner, they could easily establish partnerships that put the US at a lot of risk.
To make matter worse, they have a huge population they can toss into a meat grinder of a conflict, while the US public will quickly turn against military action with groups like Mothers of America crying out about their kids being killed to protect the rich 1%'s interests.
Then they're is Trump... that guy is just begging for an excuse to toss a nuke. His ego dictates that he have the gloating rights to say he was the first world leader since WWII to have the ball to toss one. If that kleptocrat doesn't partner with China to rob us blind, he'll start a war with them "to make Merica great again"
China has nothing to fear, they own our debt and we've already outsourced all our manufacturing to them. They more a threat to us, then we are to them. I suspect they know this and are just smarter then previous governments. They know they don't' need to beat us in a military fight. They can just slowly buy the nation buy assuming all the debt and undermining the economy. Once it collapses, they call the debt and own America.