Credit where it's due, by luck or judgement, this 'regime change', coupled with the change of management in Venezuela, will significantly impact the availability of fuel in Russia and to a point, China.
Yes definitely China. This is part of Trumpy's plan to contain China, to restrict their fuel supplies and as you rightly point out was one of the reasons to go into Venezuela. Xi is nervous about this and has already told Iran to reopen the Straights of Hormuz.
Russia no. They have plenty of their own supplies and as long as they can keep their refineries working they will have no problems with fuel availability. Zelenskyy might have other ideas though.

Had we been involved from the get go, things may well have been done by now...
I assume this is tongue firmly in cheek?
