Iran's Seyyeds have a "Black Night"

reportonbusiness.com: Iran's gasoline imports prime target for sanctions:

"Thirdly, target countries often get help from so-called 'black knight' allies, who undermine the effectiveness of sanctions and grow rich in the process. And finally, sanctions may drive wedges between the economic interests of allies who share the same policy goals."

China is the Seyyeds' "Black Night". So will the US government, or can the US government actually influence US and other world corporations to stop trading with China? Stupid question really.