A US test sounds plausible, but why would they do it so close to our own coast that its visible to land based civilians? Why not take it out to sea farther so no one is watching?
Depends on what they're testing, I suppose.
For example, if they've got a set of land-based sensors and other capabilities that they want to test in the context of certain attack scenarios, then they pretty much have to do the test in view of the general public.