Many people point to the Sri Lanka port as an example of debt diplomacy. But what they fail to mention is that Sri Lanka is the ONLY example, that Sri Lanka is happy with the outcome, and that China recently cancelled debt payments for many African countries.
What they want is to leverage the power of a (well-run) hybrid command/market economy, huge population (larger talent pool), and power of being unsuspecting #2 and slowly absorb all the other countries and economies.
The US does this too, but at least we also want to spread democracy, so the people have a say.
If they can achieve the above, they will take control of the world.
As for US spreading democracy, you should read up on how they overthrew Iran's democracy and replaced it with a dictatorship that suits the US interests better.
Why are they in Africa and selling advanced surveillance technology to countries?