Why the U.S. Navy mounted anti-aircraft guns on cranes

Was the U.S. Navy unique in mounting early anti-aircraft guns on top of cranes?

No: all navies sought high, stable gun positions, but American cranes were unusually suitable while other fleets used different locations.

The underlying practice was not uniquely American: navies looked for any sufficiently high and stable position from which an anti-aircraft gun could work. Large, rigid U.S. Navy cranes happened to provide such a platform on some ships. Other navies often found more suitable superstructure positions and therefore did not need the same conspicuous arrangement. The moment shows how a shared tactical requirement can produce a nationally distinctive installation because ship layouts differ.