Besides, China would need to grow its power a lot to even be able to fit the same tier that US does today. And if they can't or don't want to, then the end result is likely a more decentralized world. Not every era is "Pax ..." - there are long gaps in between the fall of the old empire and the rise of a new one.
People still remember Soviet-style "social harmony" and there's a big allergy for that path.
Rapid growth is not exactly popular too for multiple reasons.
Growth-over-ecology brings bad memories from soviet era
Growth-over-labour-rights brings bad memories from 90s and somewhat soviet era
Rapid change itself brings bad memories from 90s and 00s too
OP was claiming "The US doesn't look like the most powerful country in the world, nor as a leader.". If US doesn't count for him.. I'd say China is 3rd world country compared to US.