17 U.S. Code § 120(a): "The copyright in an architectural work that has been constructed does not include the right to prevent the making, distributing, or public display of pictures, paintings, photographs, or other pictorial representations of the work, if the building in which the work is embodied is located in or ordinarily visible from a public place."
There is, however, an exception for secret military installations in 18 U.S. Code § 795: "[...] certain vital military and naval installations or equipment as requiring protection against the general dissemination of information relative thereto, it shall be unlawful to make any photograph [...]"
In general this is called "freedom of panorama", and applies to lack of copyright protections [1]. Jurisdictions that has freedom of panorama will still often have national security provisions restricting specific views.
Is there not even restrictions on military bases?