Hilton Budapest, Hungary (possibly, I see the points were added the following month, but don't recall if I had to request them)
Hilton Athens, Greece
Hilton Melbourne, Australia
Hilton Sukhumvit Bangkok, Thailand

My stays at the last two were arguably within months of their opening, and the situation may have been corrected since.

Between the hassle of claiming missing points ('those are not Hilton hotels sir...'), the uncertainty of getting them at properties where I haven't used the HH card previously, the devaluation of HH points, and the 2.7% forex fee, I find myself using it only in the US, and at the rare inexpensive overseas one-nighters where the 500 points bonus tilts the balance in the HH Amex' favor.