This isn't true at all. I worked for a long time on the first implementation of the Navy's Maritime Domain Awareness System and my wife currently works for the

This isn't true at all. I worked for a long time on the first implementation of the Navy's Maritime Domain Awareness System and my wife currently works for the NRO's Enterprise Collection Orchestration system that auto-tasks orbital surveillance platforms in response to automatically detected global events. Many of the capabilities are classified, but I can assure the US Navy both knows about and has some means to respond quickly (not necessarily by dispatching a manned vessel) to anything bigger than a driftwood log that appears on an Earth ocean. The reason they don't is the Navy is not a law enforcement agency and this is not their mission.