Jack Lew, speaking at the Brookings Institution in July, confidently assured that Americans were immune from weakening markets in China.

"I will say that China’s markets still are pretty much separated from world markets," the secretary of Treasury, said. "They’re, obviously, moving towards being more integrated, but right now they’re not."

"So you’re not going to, I don’t think, see the direct linkage there," Lew said.

"I think the concern, that is a real one, is what does it mean about long term growth in China.”