Just wait until the US stops being a superpower. It's inevitable.

What two superpowers?

I'll assume we're talking about the USA and China here.

It may sound reductive, but a peaceful coexistence between liberalism (aka capitalism / other ideologies where private property rights are enshrined) and communism (in this case used as a blanket term for ideologies which are against the concept of private ownership of the means of production) is not stable and will inevitably collapse.

All that needs to happen to avoid a war is for the US capitalist class to keep their grubby greedy hands to themselves. They can't do that though, for capital must grow. They must find more raw materials, more human labour, and more consumers to maintain their profits. They are incapable of cultivating good relations with anyone, let alone anti-capitalist and anti-imperialist entities, because every relationship they enter into is an economic one in which they want to be the exploiters, the winners, extracting obscene wealth from the losers.

The rest of the world is moving in a positive peaceful direction, but I'm concerned about what the capitalist empire will do as it becomes more and more desperate. It's already done some of the most horrific things in human history while in a position of unchallenged or nearly unchallenged hegemony. I can't imagine what it will try when it realizes it's about to lose everything.