China has visible problems already:
Time is not on China’s side. There are numerous examples of this. One of the more obvious is the shrinking Chinese work force. While overall population increased 7.1 million in 2014 (to 1.37 billion) but the working age population declined 3.7 million (to 915 million). The number of Chinese over 60 increased 10 million to 212 million. All this began in 2014 and will continue for decades. The biggest problem, though, is the growing shortage of workers. As the population ages, all those one child families means there will be more elderly than the economy (and the shrinking workforce) can effectively support. Currently there are 11 working age Chinese for every retiree. By 2050, there will only be two for each retiree. At that point, retirees will comprise 30 percent of the population (versus 13 percent now.) Traditionally, children cared for their parents in multi-generation households. That model is dying out, and China is faced with huge pension cost increases at the same time they expect their economy to be the mightiest on the planet. But at that point, the largest single government expense will be the care of the elderly, and this will impose crushing taxes on those of working age. Many working age Chinese are worried about this, for there is no easy solution in sight. China tried (in 2013) to relax the one-child policy but the newly affluent Chinese are less eager than earlier generations to have a lot of kids. To make matters worse there is not much in the way of pensions or health care for most of the elderly to begin with. The government recognizes this is a real problem but does not, and will not have the cash to deal with it.
I've noted that even if China continues to gain ground on us, even passing us by, by 2050 we may reach peak China and see fifty years of America clawing back lost ground.
We have problems. But I wouldn't trade our cards for any other nation's hand.