US WAR IS NOT WITH IRAN.
US WAR WAS NOT WITH VENEZUELA.
The US war is just with one country.
"China."
For years, China has been taking cheap oil from 2 sources.
Iran and Venezuela.
Before the Venezuelan takeover, China absorbed between 50% and 89% of Venezuela's total crude oil exports.
Much of this trade was conducted through a "shadow fleet" and often rebranded as originating from countries like Malaysia to evade U.S. sanctions.
And here's one more thing.
Most of the China-Venezuela trade was happening in yuan, which was dragging dollar dominance down.
If talking about Iran, China purchased more than 80% of all Iranian crude oil exports last year.
Iranian oil typically trades at a steep discount of $8 to $13 per barrel below the international Brent benchmark, which allowed Chinese refiners to save an estimated $10 billion in a single year.
And just like Venezuela, the China-Iran deal was happening primarily in yuan too.
As per some estimates, China was importing 20% of its crude oil from Venezuela and Iran, bypassing the USD.
And the US is trying to break this.
That's why China has been criticizing US decisions against Venezuela and Iran.
Today, China officially opposed US and Israeli military action in Iran and also pushed Iran to reopen Strait of Hormuz.
China knows that if the war continues and US gains control over Iran's reserves, it'll have to do trade deals in USD, which will weaken its dominance.
On the other hand, Trump's focus is to make China as weak as possible because 
there can't be 2 global superpowers.