>I don't think different political ideologies imply adversarial intentions

Your source could be human conflict for all of recorded history.

It's not primarily ideological, it's geopolitical realism. They are a growing economic and military power in a different geographic sphere, competing over global influence and power. The history of civilization is conflict over scarce resources, space, and power. China is a cohesive ethnic and political collective and nation that exists separate from the US, it's government and citizens.

Of course there is and will always be room for co-operation in many areas; economic trade is a big one. But conflict over competing interests is a fact of life and where that comes into conflict global adversaries and enemies are created.

"Morality" is not a good metric to guide geopolitics, where material national interests and power dictate more than anything.