You could ask the same question about Trump. I think there are many reasons. Perhaps the simplest reason could be political: American voters do not like China because the Chinese are now running the factories the Americans used to run a few decades ago, even though that's more the fault of American politicians than the Chinese obviously. Another one is because they align themselves strongly with the Israel/banker lobby, so naturally a country that challenges them is against the interests of their supporters and donors.

Finally, keep in mind that even the nationalist, traditional-minded China that is rising would not be necessarily aligned with the US interests. They would be competing empires, and while that doesn't necessarily mean hostility, it does imply some competition. I think that when and if the US manages to escape the grasp of the (((globalist cabal))) (which might take more time, the US is basically home turf for the cabal) the relationship between America and China will shift away from outward hostility and towards productive competition.