Harnett,
Thanks for this link. So, it's all down to the excessive cost of healthcare - double the developed country average!
The article also shows how it's important to be realistic about the deficit/debt problem. The USA is borrowing at negative real interest rates short term and zero long term. The UK government is borrowing at negative real interest rates short and long term! Are these signs of fiscal crises? No, they are signs of economic crises!
I recently read an article that said that if the US actually enacted all the legislation on the statute book and allowed all temporary measures to lapse, the (apparent) deficit problem would disappear (although the results in terms of services and transfers would not be pretty). Unfortunately, I can't find the reference again!