> Russia: dictatorship. Cuba: dictatorship. Iran: theocratic dictatorship. Venezuela: dictatorship. North Korea: dictatorship. Syria: dictatorship. Sudan: recently a military junta.
I read it as: Russia: enemy ex-superpower, second biggest net oil exporter. Cuba: stole our oil refineries half a century ago, we're still mad about it. Iran: in top 10 of net oil exporters (also, tried to take them over and fucked up). Venezuela: top ten of net oil exporters. North Korea: old enemy, though also universally considered evil. Syria: US wants to force a government change and supports the rebels; there could be an indirect oil-related angle in here.
It may be that I've just been reading too much about energy economics recently and am getting all consipracy-theorist. Even if so, I absolutely don't buy that there's any higher good for any of those sanctions.