Today's NYT:

What $1.2 Trillion Can Buy

The human mind isn’t very well equipped to make sense of a figure like $1.2 trillion. We don’t deal with a trillion of anything in our daily lives, and so when we come across such a big number, it is hard to distinguish it from any other big number. Millions, billions, a trillion — they all start to sound the same.

The way to come to grips with $1.2 trillion is to forget about the number itself and think instead about what you could buy with the money. When you do that, a trillion stops sounding anything like millions or billions.

For starters, $1.2 trillion would pay for an unprecedented public health campaign — a doubling of cancer research funding, treatment for every American whose diabetes or heart disease is now going unmanaged and a global immunization campaign to save millions of children’s lives.

Combined, the cost of running those programs for a decade wouldn’t use up even half our money pot. So we could then turn to poverty and education, starting with universal preschool for every 3- and 4-year-old child across the country. The city of New Orleans could also receive a huge increase in reconstruction funds.

The final big chunk of the money could go to national security. The recommendations of the 9/11 Commission that have not been put in place — better baggage and cargo screening, stronger measures against nuclear proliferation — could be enacted. Financing for the war in Afghanistan could be increased to beat back the Taliban’s recent gains, and a peacekeeping force could put a stop to the genocide in Darfur.

All that would be one way to spend $1.2 trillion. Here would be another:

The war in Iraq.

I ran across an interesting little stat a while ago. If you add up our military expenses since WW2 it is almost exactly equal to the national debt, around $10 trillion. So it seems reasonable to me to say that of all the money we've spent on the military, we haven't paid for one red cent of it. (and we never will)

Yes but in the high tech twenty first century every year is a decade, or even more than a decade. Entropy is exponentially faster, and empires look almost like claymation compared to ancient Rome.

Key difference is that Japans government borrows from it own people whereas the US is mostly borrowing overseas today. So it is likely less sustainable. Given the state of the Japan economy over the last 2 decades I really think that if you have bring them up as a comparison you are in a bit of trouble.