As far as I'm aware, China has been giving loans to various countries in Africa and building infrastructure in exchange for money and maybe some stuff like recognizing Taiwan as part of China. But why do people say China is imperialist for doing this? Is there truth to it or is it another strain of radlibs eating state department propaganda?
You really just need to spend some time reading and learning about imperialism, because you're incorrect about what that word means. Try reading Lenin's Imperialism to learn more about it. There's far more to imperialism than "trying to increase your power"
I agree with Lenin's description of imperialism. Essentially, finance capital is created in a country and expands to other places, where it becomes dominant and everything there is subservient to it.
However, I don't think its wrong to say that a government ceding its hegemony, in whole or part, would be an example of imperialism, independent of Lenin's description.