While Avatar The Last Airbender and Legend of Korra aren't animes (made in the U.S.), they still have many similarities and are two of my favorite shows.
Actual animes:
Full Metal Alchemist Brotherhood (one of the best animes, seriously if you haven't seen it, watch it)
Full Metal Alchemist (also good, but I enjoyed brotherhood more)
Naruto + Naruto Shippuden (full of fillers, but I've loved Naruto since I was a kid)
Fairy Tail (recently discovered it, love the show. A lot of humor, great characters, great fights, really is a great anime)
Death Note (little darker then the others and is all psychological thriller, no fighting, but is an amazing anime)
Update, watched some more animes recently so:
Knights of Sidonia = fantastic anime
Sword Art Online = amazing anime (may be my new favorite)
Psycho Pass = pretty good, interesting anime
Attack on Titan = also really good











