He was quite useful and likeable rotation player up to a year ago. Was scoring useful goals and being energetic, and mainly being backup or rotation.
Then he got an injury, came back couple months later, and the offensive box to box impact that hid his extremely limited game was no more.
Plus Allegri making him a nonstop starter despite awful performances, just recipe for disaster. His limitation technically and passing became extremely glaring the more he played past year, as was the fact he is not a ball winner at all.
Prior to that was easy to like him or think he is a useful depth player.
Him being an American had no factor in being disliked (except for likes of alen). If anything made him more interesting, different kind of charming child like personality to the mix. Meme worthy ones as we saw in the documentary lol
But at end of day you get judged on your football ability, and his was quite frankly limited to terrible degree. Unless he was playing as an emergency AM just making off the ball runs into the box, he had no tangible use on the pitch.