Bald comes from the old word balde, meaning white, and as you probably know Bald Eagles have white head and tail feathers. So Bald Eagle basically means White Eagle.
Yes, in fact, it is the bird of the United States, and is protected by federal law, so if you poach one in the United States, then you are in big trouble.
To date the largest species of Eagle would be the Philippine Eagle (Monkey Eating Eagle) from the Philippines and neighboring isles. The second largest would be the Harpy Eagle.