Just as a note - you *can* file for a copyright if you want to - it gives you added protection! I have the steps here - http://www.lisashea.com/workfromhome/rights/copyrightfiling.html
this puts your drawing, photo, writing or whateveer on file with the US Copyright Office, which then has reciprocal arrangements with other governments' offices. You don't have to go file your work with every single government!
It's well worth it if you are an artist who is worried about people stealing and using your work!