Its actually pretty even.
First, lets address elections. Last one, a Dem won. Before that, Bush won because he was an incumbent during a war, and traditionally, that all but guarantees your success: however, the vote was obscenely close. Close enough that you can't reasonably say that there was a significant difference. Election before, a Dem one. Yes, Gore beat Bush. But because they cheated in Florida, and the electoral college is dumb, Bush was shoehorned in by the Supreme Court. The 2 before that, a Dem. But all of this gets thrown out the window, along with all the conservative presidents before, when you realize that less then half of the people vote. An election is a measurement of how a party can mobilize there base, not an accurate representation of the breakdown of America. As it turns out, religious zeal is more effective then optimism when it comes to getting people into the voting booth.
Next its worth pointing out that in most issues, Americans lean a bit towards liberal. Republicans fundamentalist bent has roped in a lot of religious moderate lefts without them even realizing it. And also, Republicans have done very good with PR, and tend to present a very loud, single, unified voice, while the Dems are more fragmented.
And lastly, you can't really say its a conservative country because in many places, that just doesn't make sense. Yes, go deep into Texas and your going to see the conservative America stereotype you hear about. Go over to California, or up into New England, or basically into most any population center, and you will find people more Liberal then you. In my neck of the woods, you could say something like, "At least we got that asshole Bush out of the Whitehouse", and you are way more likely to offend for useing the word asshole then hating Bush. Some of my local politicians ran there entire campaign by pretty much not presenting any platform except, "My opponent likes Bush, and I hate him, vote for me".
Overall, the split is pretty 50/50.