The one big problem, though, is that China does not believe in freedom. At all. Censorship, no free press, no freedoms of opinion, expression, religion, etc. And they see nothing wrong with that. Whenever the US hurts these freedoms, they get criticised, even by their own people, and they eventually back down.
The fact that the US promises freedom but constantly breaks that promise makes them hypocrites, but it also always has the option that they will get back to their promise. China does not see the point of freedom at all, and considers it dangerous. And that's terrifying.
If we're going to have a superpower, I would love a China that respects freedom in that role. They would be better at it than the US. But current China is not that China.
As flawed as the US is, they at least have that going for them (pre-Trump US, at least). Though ideally, the EU would step up. They don't seem to want to, though.