I am preparing to sail to Panama
in April and to clear in there one needs to present his clearance papers from the last port of call. Checking the Customs
and Border Patrol website there is no information about leaving the US if you are a US citizen in a recreation vessel. Last couple of times that I cleared into the Bahamas
they did not ask for a zarpe from the US. It seems logical that if you are leaving your home country your normal boat registration
should suffice in a foreign port.