The security people at the Panama canal get a little "twitchy" about Dynamite so that's a no. Otherwise, no license required except to go offshore. Then your captain takes care of it. In NC it's easy to get a visiting permit btw. I've been fishing out west and it was pretty easy too. In Utah for example you just visited your nearest sporting goods store and filled some paperwork. Good trout fishing up in them Utah mountain lakes.

Central America is pretty relaxed about fishing licenses. I've even just taken a "Cayuco" (dugout canoe) for kicks and actually caught some Peacock bass on crappy department store tackle purchased down there. Hard to come by nice rods though as the locals just use a bunch of 30 pound line spun around a plastic spool with an old piece of rusty metal for weight, swing it above their head and let go. Not as much fun as a rod but effective if you just need dinner.