Ed Stetzer, President of Lifeway, said- "...making the gospel known is more complicated in America today than it was in decades past. Less people today have a general Christian orientation, or even a shared Judeo-Christian ethic. This means concepts (truths) like sin, death and hell cannot be assumed..."
As a result of this, I think proclaiming the gospel is easier, even though it is more complicated. The reason is (to borrow Matt Chandler's terms) many more people in our culture have not been 'inoculated against the gospel' as in the past. In my experience, it has been easier to argue for the holiness of God when coming from the idea of the fallen nature of man. When the 'bad news' is assumed, as it used to be, sometimes the good news gets lost in the moralism (legalism). Since our culture no longer assumes any bad news, this part needs to be a component of the gospel message, and as Chesterton said, sin is the one part of the gospel that can be empirically confirmed...people don't need much convincing of the fallen nature of man, even though culture tells us we are all basically good.
The hard part comes when we confront the culture with our fallenness. If there is one sin that can be committed against a culture that laughs at the concept of 'sin', it is the sin of destroying people's self-esteem. Self-esteem is a god to many individuals and institutions in our culture. But we can't proclaim the good news of Christ without first breaking down the primary enemy of the gospel- self-righteousness. Self-righteousness and self-esteem are the gay-marriage partners of self-actualization, which can be seen first in scripture in the garden of Eden (you remember the part with the snake and the naked lady, right?).
I used to worry a lot more about how secularized our culture and country are becoming. I don't do that so much any more. When Uzzah made the mistake of putting out his hand to keep the ark of the covenant from falling off the ox cart, he assumed that his hand was less contaminated and desecrating to the throne of God than would be the mud on the ground below. In the same way, I assumed our 'christianized' culture was better off than our secularized culture. Wrong idea. Both are in the same danger of the same fires of hell.
And as the culture becomes more secularized, it is sure getting easier to demonstrate a difference between the profanity of culture (and those who live in it) and the holiness of God.