The Founding fathers were human, fail-able, flawed. Some of them were slave owners, for example. The Constitution itself has been amended over time, and follows on from documents such as the Magna Carta that was written in 1215. As such, they were perhaps christian, but they didn't live a christian life, imo.
Believing in a God and after life is very tempting. Who doesn't want to go to heaven after this long journey and meet our loved ones? However, the idea falls apart the more you think about it. I don't believe in the supernatural, so that's a real problem. And what kind of father would send their son down to be tortured and killed - was there really no other way to make his point?
Saying that, part of life is accepting that there are things we simply can't know. Was there a Big Bang? What was before the Big Bang? If there's a God, it stands to reason he had to come from somewhere, he had to have a start. But apparently no, he's simply always been. Children suffer, disease, and honestly when you think about it, our very bodies aren't designed all that well. One orifice for drinking, eating, and breathing? It's asking for trouble!
What's vital, is tomorrow. That you treat everyone you meet with respect. That you help those that you can. That you do no harm to others. That you spread love and kindness. Tomorrow could be my last day on Earth (we're all oldies here) and I want to leave it with a good conscious. If I'm lucky, I'll have another 20 years on this planet. Then I become one with it. Every day we wake is to be celebrated.
ps: Some religious music is very very nice!