Definition of imperialism: The extension of a nation’s authority by territorial acquisition or by the establishment of economic and political dominance over other nations.
Definition of hegemony: The dominance or leadership of one social group or nation over others.
I would be a little more nuanced with my definitions personally. I think Russia is textbook imperialist. I think China is borderline imperialist, and I think the USA is more hegemonic.
I think all 3 play all the same games except that the USA doesn’t play in territorial expansion, which for me is a big improvement over those that do.