They have two broken legs and the US only has one.
The US does also have massive unfunded pension committments. Not all of them are currently government pension funds. There are many company plans that are not properly funded and can't be supported by current incomes. As they fail the burden is placed onto the federal government via the Federal Pension Benefit Guaranty Corp.
The figures for the "national debt" can't really be trusted because of the way it is accounted for. The debt only includes those bills that have come due and the government had to borrow to pay. It doesn't include all of the bills that todays actions will cause in the future. If they order 100 aircraft, for example. All governments hide the true extent of the debt (with the posible exception of China). Some may be doing a better job of hiding it.