So no, the US are definitely no more allies of Europe than China is.
You have no sense of proportion. China lives by completely different rules. They have no respect for freedom of speech or democracy, quite the opposite, and they don't care if other countries do. The US has its flaws, but I'll take a flawed democracy over an oppressing dictatorship any day.
And beyond ecinomics... well, if you're European, it's not like China is out to burn your home, rape your wife, kill your dog. They're on a different hemisphere for chrissake, there's noting to gain for them from indaving another, regardless of whether that's Europe or US. (FWIW, the only country that has a habit of doing that post-WW2, regularly, is the US.)
No, maybe they'll just destroy all your infrastructure that's connected to the internet, including telecommuncations, power supply, and everything else that's needed in a modern society. Japan's being in a different hemisphere didn't stop them from starting an all out war with the US. If the western countries tries to do the right thing and stop China from taking areas from smaller countries in Asia then a war is not an impossibility. I assume you know that China is already doing that by creating artificial islands with military bases.