Wow. The US net debt is a really huge number. How on earth did it get up to that?
They need money to invade sovereign nations such as Libya, Serbia and Iraq, right? Also they are spending almost $1 trillion a year to maintain their war machine. That said, most of the federal debt was amassed after Barack Obama became the POTUS. And if Hillary becomes the next POTUS in 2016, it can rise to new peaks.
Financing war is only part of the budget. There's also medical insurance, but since the average American is more than 10 times richer than the average Russian, bankers will always have more trust in US than Russia. US government can borrow money at less cost than the Russian one, and this isn't going to change in the foreseeable future.