This month, Russia and China are sparking new jitters in Washington. That is primarily because of their stage-managed displays of diplomatic unity, around Ukraine and much else. But it is also down to money: during a visit by Xi Jinping to Moscow last week, Vladimir Putin pledged to adopt the renminbi for “payments between Russia and countries of Asia, Africa, and Latin America”, in a bid to displace the dollar. And this comes as Moscow is already increasingly using the renminbi for its swelling trade with China and embracing it in its central bank reserves, to reduce its exposure to “toxic” — American — assets. Does this matter? Until recently,…