China is already at war with USA, i.e. the Trade War. Import of Iranian oil would just be a small battle. If US wants to escalate the trade war fully, it will be a trade world war with all nations on Earth affected one way or another.
Two camps will emerge if a trade world war erupt, one camp for the global trade the other for the protectionism. We can already see the embryonic stage today who will join which camp.
However, the mad Orangeman may not be that mad enough since basically he is still a businessman trying to make gains in carrot and stick negotiations, though his B-Team has more war mongering agenda and that could be bad news if Trump cannot control them.