While the US does have an enormous amount of debt to these countries, you left out the fact that they also owe us a gigantic debt which doesn't get factored into the "we owe people money!!@!@!2121" equations. We've loaned trillions to China, Japan and other countries.
America hasn't loaned other countries 'money' they've loaned them government bonds and paper money which are worthless, China in particular has been quietly buying up lots and lots of precious metals for a long while now, while Americans have been arrogantly doing nothing, convinced in the superiority of their dollar.
China is using dollars to buy things like gold, which is traded in terms of dollars. They are still, for the most part, relying on the dollar for the majority of their assets.
China is also a net creditor to the US in the amount of Trillions of dollars