They're not going to be evenly spread out over the continent. Zimbabwe and South Africa have a good portion of the mineral wealth that they're interested in. When whites controlled Rhodesia (which became Zimbabwe) they were able to do it with a white population of just 270,000 controlling 6 million blacks at a ratio of 22 to 1. They only lost control due to external sanctions and external support for black rebels.
If the Chinese decided to take over control, they would only need enough Chinese men to hold the ports and airports long enough for a few million reinforcements to arrive. If a port was being held, the Chinese could quickly insert a lot of men and military supplies using their fleet of cargo ships.
Transporting a few million reinforcements isn't going to happen willy nilly. I doubt even China could do it overnight short of war time readiness. But your point is well taken, in that in a continent like Africa, where the local population has a difficult time uniting their resources, it would be difficult for them to push out the Chinese if the Chinese insisted on staying. And the 800 million Africans live in many separate countries. And even within those countries, the local people population would have a difficult time marshalling their resources.
Wheras in the US, if Americans wanted to forcibly remove 10 million illegals, it can happen quickly. Resources can be mobilized quickly in the US, provided there is political will. In Africa, the ability to marshal resources, let alone doing it quickly, is nearly non-existent.
But honestly, I really doubt China has coloniel ambitions in Africa.
You might be right. The Chinese would be a lot more ruthless that our norm, anyways - Probably somewhere along the line of the Belgian Congo. So they’d be able to control more area with fewer people.
In any case, Chinese control of Africa could only improve Africa.