Oil producer != oil power. What matters is the ability for a government to routinely influence prices. The US government could, in theory, ban all exports or manually dictate production but we tend not to do that (yet). Our main government price-control lever comes from SPR releases, but we're nearly tapped out. China has no real legal restrictions on what its government can dictate except for what makes sense geopolitically, so at any moment it can make oil vastly cheaper or more expensive, even moreso than OPEC can by manipulating supply.