The main purpose is probably to get American ships to fire the first shot, and thereby firmly establish that it is the U.S. empire that is the aggressor.
I see your point, but it's kind of one thing to blow up a handful of "drug boats" (only a complete idiot believes that story, but simply having _any story_ seems to be the only requirement these days), quite another to start going after tankers carrying oil or their escorts.
Maybe they'll try to arrange some kind of Gulf of Tonkin style false flag.
Are you seriously claiming that the the boats blown up so far were not smuggling drugs? I think that sinking them was bad policy and possibly illegal, but I know enough about boats to be pretty certain that those guys weren't out there fishing.