Friendly fire is a terrible thing to be a casualty of. But such things happen in the battlefield. As has indeed been happening in the Iraqi war zone.
It can also happen in the world of economics. Even between parties who are not presently engaged in warfare, economic or otherwise.
The United States and Japan are friendly nations. Indeed, in Junichiro Koizumi's terminology, international cooperation seems to be the same thing as endorsing whatever the American president says. Friendship cannot get much more loyal than this, even if those endorsements tend to come rather late in the day when all is fait accompli and the loyalty does not count for much anyway.