The pirates don't know which country owns these ships. Heck these ships have so many "layers' of ownership the owners don't know who owns them. They also often have multi-national crews.
I think the reason these ships were caught is the pirates are having to go out 250-400 miles into international waters and also the piracy is up what 500-600% over the years? It was just a matter of time an American ship was hijacked.
Now, we'll see what the obama response is.
The pirates know we have a cheese-eating surrender monkey in the White House, expect these types of incidents to continue for 4 years.