Paul Crowley: remember that US markets are much larger than, say, the US economy. From the article:

It depends on the comparison. U.S. GDP is $12 trillion, the total value of traded securities (debt and equity) denominated in U.S. dollars is estimated to be more than $50 trillion, and the global value of traded securities is about $165 trillion.

And $10 trillion isn't where they are now, it's where they will be in four years or so. So while it's a bloody large amount of money, it's unlikely to be more than, say, 5% of traded securities on the market. And that doesn't include stuff like currency holdings.