Can a non-US first tier subcontractor working on a US-embassy project in Europe file a claim under the Miller Act or does the Miller Act only protect US-subcontractors?
If a Miller Act bond was provided then the location of the work itself does not matter, other than finding the right US District Court in which to file the lawsuit. Be advised, however, that the Miller Act allows for a waiver of the bond requirement for work overseas in the event providing the bond is "impractical" - so your first step would be to inquire as to whether there is a Miller Act bond for this work. Please feel free to contact me directly if you need any additional assistance.
A claim against a Miller Act payment bond can be brought by anyone furnishing labor and materials to the project - there is no specific requirement to be a U.S. citizen or company. I have routinely represented foreign companies in US lawsuits and arbitrations.