how about noble , robust, swift, clever, mighty, royal, soaring ,commanding , impressive, proud, dignified, glorious, feral, untamed, majestic, imposing, magnanimous off the top of my head
as for quotes how about
1- As the eagle was killed by the arrow winged with his own feather, so the hand of the world is wounded by its own skill.
2- Fool that I was, upon my eagle's wings I bore this wren, till I was tired with soaring, and now he mounts above me.
3-"The day is done, and the darkness, Falls from the wings of Night, As a feather is wafted downward, From an eagle in his flight"
Henry Wadsworth Longfellow quotes
4- A believer is a bird in a cage, a freethinker is an eagle parting the clouds with tireless wing"
5- The Eagle, he was lord above"
William Wordsworth quotes
6-"From the oyster to the eagle, from the swine to the tiger, all animals are to be found in men and each of them exists in some man, sometimes several at the time. Animals are nothing but the portrayal of our virtues and vices made manifest to our eyes, the visible reflections of our souls. God displays them to us to give us food for thought."
Victor Hugo quotes
7- "Methinks I see in my mind a noble and puissant nation rousing herself like a strong man after sleep, and shaking her invincible locks. Methinks I see her as an eagle mewing her mighty youth, and kindling her undazzled eyes at the full midday beam."
John Milton quotes
i don't know about the songs but i think i remember one to that effect it's called the wind beneath my wings
hope i was of help
well... i guess from your list you have a lot of words.. ( in my opinion that's a lot) you could use majestic, power, unity, um... well you're right it's hard to think of these words lol um... well the eagle is meant as a symbolism for the United States Of America's government and the power that they have, it represents i guess the American justice system if i were you I'd look up the American government and find out why the eagle is a symbolism because i write lyrics myself and I know very well that lyrics must have an inspiration and a meaning that isn't just on the surface but they should have a deeper meaning too.. which is how lyric analysts are created... like me.. and im still in school lol.. but yea look up a background and you just might find inspiration for some words good luck too!