I would say we used identify as a whole, when everyone was united and proud, but as years go on people start forming different opinions and beliefs, that people will judge other people over which in the end people aren't going to want to identify as, so people will stop saying they are apart of a certain group of "Americans" and start acting like individuals rather than a group, it separates us a society and country.
(this is just my opinion, I'm very sorry if it doesn't help!) Good luck on your essay :)