One of the great values respected in America is the freedom to critique ourselves as a nation from the inside. That is what keeps a community aware of its own tendency to be corrupted, and our country, like any nation, needs that internal critique. Our founding fathers, I think, understood that well.
The critique is necessary precisely because "the American dream" is a mythical idea having less to do with one particular "dream;" rather, it alludes to the preconceived dreams each person brings with them into a cultural space that allows various freedoms of expression. A few (oversimplified) examples: If you're a Christian (or any religious person), your dream is the freedom to practice your faith without oppression. If you're an entrepreneurial capitalist, your dream is the freedom to attempt to make lots of money, with almost no restrictions. If you're poor, your dream is - ostensibly - to climb out of poverty. If you're gay, your dream is to be allowed to love without being condemned. And so on.
Ironically, our freedoms in the United States are typically so vast as to make some dreams seem almost comical -- for example, culturally hip kids wearing mass-produced Che Guevara t-shirts. Think about the many levels of irony there... :-)
So, my point is, since we are a nation that prizes ourselves (in most cases) on the freedom which draws into our midst many different varieties of people - and just as many takes on the "American dream" - we as a society have tried to find a way to allow as much freedom as possible, for as many people as possible, without rampant abuse. And that is obviously not easy.
But what's more, it highlights what I take to be a more important point: Any type of over-arching "meta-dream" (if I can coin a term), for example, Christianity, will gradually lose influence in this type of society. It's inevitable. Why? Because as more worldviews come into play, the less monolithic any one worldview can be. This does not lessen the value or truthfulness of Christianity. It simply is the way things are in a system that prizes personal autonomy and freedom of expression above all else.
Christians need to stop kicking against a system that is ultimately working against them, and follow Christ - I mean, really follow Christ, living as he lived - regardless of what the social, political, or economic system may be. This does not mean we aren't involved in those systems, seeking to redeem them whenever we can. But we must be VERY careful not to confuse reforming and redeeming. We mustn't conflate reforming those systems with bearing witness to God's Kingdom. We must not place our hope in the American dream. Because if our hope is placed in Jesus + America, that is idolatry. Christianity supersedes and critiques all systems. And too much of what we call Christianity in this country looks suspiciously like systematic idol worship.