Nobody appointed the US leader of the world, what are you talking about? It's just a matter of "whoever is most powerful and influential". There's no war needed, and the US never conquered the planet.
I'm not doubting that China is the likely eventual successor, I'm doubting that they can succeed anything at this particular point in time. Nobody wants China in charge. It would make any issues experienced with the US in charge like a joke. Maybe once their dictator dies?
Yes, China is a likely eventual successor and in some parts is the world has replaced the US in being the influential superpower.