Well, the isolation assumption is a pretty weak one, but taking it, if China won, then why wouldn't Europe want to buy from them? Economics always beats hard feelings.
If China won would assume Europe would stay out of the conflict while the US and China fought each other. A fight with China as the enemy would probably end up dragging in basically the entire 'Western' world.
Of course, it's all pretty insane to speculate about, since:
A: Most countries now seem like they're trying to avoid actual wars as much as possible, and most remaining issues seem to be sparked off more by extremist nutcases/cults than a country's army trying to invade or fight off another.
B: The US, most of Europe, China, etc have nuclear weapons, so any actual war between any of them would probably end like everyone's worst fears about the Cold War made reality. Don't think there'd be much trade or economics left after that.
The US never has to surrender - they simply say we will use our nuclear weapons. These wars have no victor hence these wars have been replaced by proxy wars in various locations.
That's why Russia now focuses solely on disrupting elections and cyber warfare-only from within can these nations be affected and weakened.
Of course, it's all pretty insane to speculate about, since:
A: Most countries now seem like they're trying to avoid actual wars as much as possible, and most remaining issues seem to be sparked off more by extremist nutcases/cults than a country's army trying to invade or fight off another.
B: The US, most of Europe, China, etc have nuclear weapons, so any actual war between any of them would probably end like everyone's worst fears about the Cold War made reality. Don't think there'd be much trade or economics left after that.