Actually, Japan (next to Britain) is arguably the most significant ally we've had in the war on terror.
2004 the deployed a small contingency of troops to Iraq. It may have been small in size, but it was historical for the country:
This was very controversial yet despite this very important part of Japanese culture, they felt 911 was important enough to deploy troops. The first such action since WW2. And by the way, this was at the request of the US, and they complied.
It was the end of an era for the country whose policy was to not get involved in war. And they broke such policy at our request. I'd say that's pretty significant.
Meaning, they are contributing more than anyone else.
From the Whitehouse website:
The JDS Tokiwa supply ship refueling the destroyer Sawagiri
Between 2001 and mid-2005, according to the Asahi, forty seven MSDF ships have participated in thirteen rotations on station. By October 2005 MSDF supply ships had supplied 552 ships in the multinational force, dispensing fuel worth 155 hundred million yen.
Sorry to hijack, but I couldn't let the implication that Japan does nothing to help with the war on terror go by.