Not so sure about that. They've got a massive industrial base (thanks in particular to American out-sourcing). As an industrial engine, they are for this century, what the US was in the last.
As long as there are people to buy their products in massive quantities, the Chinese economy will do OK.
The joker in the deck is probably not economics, so much as politics.
China may own a large part of our debt, and maybe other countries also, but IOUs aren't worth much in fiat money.
The US only has 2 real assets. Land and people. And China has enough of their own people.