If I remember correctly, another category is US government works. The US government has before asserted that just because US law requires works of the US government be freely available within the US does not mean, in their view, that the works are PD elsewhere. They have certainly, as I recall, charged non-US corporations for using such data.
Exactly, that was one of the cases I was thinking about. A large proportion of Wikipedia's free images fall under this case. It could be an even bigger problem than different fair use laws for someone publishing Wikipedia content outside the United States.
Regards, Haukur