I'd argue that there has always been this divide, or similar divides through the course of US history. There's a rural/urban divide which has slowly but inevitably moved in the direction of the urban side throughout the last 100 years. There's a rich/poor divide which I already referenced as haves and nots. There's an educated/uneducated divide which closely mirrors the wealth divide.
None of this is anything new.
You seem to have some beliefs about US history which I don't share. I don't believe in the myth of upward mobility in the US, while there are certainly examples of this, the story is oversold. I don't believe the society is as meritocratic as it is made out to be. The biggest predictor of a person's success is their parent's wealth.
I'd also argue the fact that you apparently crossed this major divide in American culture without even realizing it suggests that maybe you didn't cross a major divide of anything at all.
This is without even going into the immigrant/religious/racial divides that exist. We aren't going to have a homogenous group of 300m people - this isn't a bad thing, and it isn't a new thing.
