It is strange that that map says the US debt is $14 trillion. It is over $18 trillion by now.
I checked the map. It is saying that all the countries have some debt, even the green ones. I wonder, then who is lending ? I mean, is there any country without a debt ?
p.s. Sorry, I'm not good in economics.
The United States issues Treasury Bonds. Anyone, including US and foreign citizens, can buy those bonds. Some foreign governments also buy them for the stability of the investment.