Japan has a total national debt (excluding local gov. debt) of 668 trillion yen. It has revenues of 92 trillion yen and annual interest of 21.5 trillion, with an annual deficit of 22.7 trillion. (Source: http://www.mof.go.jp/english/budget/e20101224b.pdf). Assuming an exchange rate of 80 yen/$ this is the equivalent of a national debt of $8.3 trillion, with an annual deficit of $284 billion, almost all of which is interest.
The US has a total national debt of $14.2 trillion, with an annual deficit of $1.48 trillion, of which $214 billion is interest.
The US's national debt is 1.7 times that of Japan (granted the population of the US is more than double of that of Japan). The US's annual deficit is more than 5 times that of Japan.
So while Japan's national debt is larger than that of the US on a per capita or GDP basis, its debt is growing slowly. Another way of putting this is while the US is not in as bad as shape as Japan yet, on an annual basis it is in much worse shape and at some point soon will be in worse financial shape overall. When this will occur is the subject of another future post.