It was created intentionally, by taking out loans. Some of these loans are owed to her own citizens, in the form of bonds. Others are loans taken from business and even foreign states. In the lattermost case, the debt creation is the benefit even more than the funds received; a nation that is owed a large sum by the US now has an interest in keeping the US around so he can repay that debt.

The US has not historically had a problem paying her bills. It is a constant concern to make sure this continues to be the case, however.