China

Even with a robust recovery, the US is on its way to losing its position as the world's largest economy to China in just a few years.  It will be a number of years after that that China's per capita wealth catches up with the West's, but as a single unit, China will soon no doubt be the richest country on Earth.

I want the Chinese people to prosper.  Heck, it is heartbreaking that any person anywhere is born into poverty.   But I think it will be troubling to know that the nation with the largest economy is a police state.  It isn't even that I fear military conflict between our two countries.  I would think that the same fear of mutual destruction that kept the Cold War peace will be in effect between the US and China.

Yeah, I know that during the Cold War the US frequently behaved badly.  But the most powerful country then was at least generally a free one, and that is meaningful when more than half of the world population lives in police states.

I also figure that America will have to adjust its national identity as it loses the top economic spot.  I don't know how this will play out, except that I imagine some ugly politics.