I think American cultural identity is increasingly fragmented and tenuous. I think that the rise of the identitarian right has much to do with this.
At the height of the Cold war, there was an enemy to define ourselves in opposition to. We don't have that anymore, and now it's just a vast land expanse of people who share an increasingly tenuous common legal and moral framework.
Personally, as an anarcho-capitalist, I'm fine with letting go of "America" as a concept. Ideals of personal freedom and liberty are greater than just one nation. And increasingly I think Americans are going to have to choose between those ideals and "the nation."