Contrary to prancing hippies and yippies at the time in 1972 (I was there at 15), today the nation is probably more liberal than ever before culturally.
I blame academia, feminism and uncontrolled immigration.
But I agree that Obama will have a hard time.
Change takes a while to spread across space and through different layers of society, but when it does, people come to take it for granted.
The first time avowed homosexuals or transvestites appeared on television to talk about their lives it looked like the whole world was crumbling. Now people take it for granted. Maybe that makes us more liberal and maybe people are wrong in being so blase, but it also means that society may have found a way to cope with something that looked like the end of the world (maybe it will be the end of the world, but people aren't as worried about it any more).
You'll find a lot more illegitimacy in the US than there was thirty years ago, but are attitudes towards adultery or abortion really more liberal than they were in some parts of the upper middle class thirty years ago? The median age in the country's gotten higher since the 60s and 70s, so there's less thinking one ought to live the way college kids do.
Morals in the country as a whole are looser and more lax, but people who say that we need more abortion or more divorce or more indiscriminate copulation or more drug-usage aren't likely to get much of an audience now. Those changes came and most people don't want to go further in that direction.
Obama does go too far into "lifestyle liberalism" for most people. But the election may be closer than it looks now. If it starts to look like a blowout for McCain, a lot of people might figure that they can stick it to Bush one last time (by voting for Obama) without it really mattering.