The Peacekeepers. Oh Say Can You See... Book 7.

Far across the Atlantic Ocean, a great pirate fleet was assembled. For the past several years, these pirates had looted the coastlines of the western European nations. Now they were turning their attention to American, and only the Peacekeepers could stop them. They plan to loot the natural resources and treasures of America. And they are coming with 5,000 ships that are armed to the teeth.