The US government is able to borrow at a low rate because there are few good alternatives: the Euro and the Yen are both terrible choices, the Pound is not part

The US government is able to borrow at a low rate because there are few good alternatives: the Euro and the Yen are both terrible choices, the Pound is not particularly good either, the Australian market is too small to absorb significant inflows, and the Chinese market is not open to foreign investment. As the Chinese open their currency over the next few years and present it as an alternative reserve currency to the dollar, the free ride will start coming to an end and the US will need a significant devaluation in order to keep from choking on the higher rates. It would be better to have the debt under control when that happens.