Being raised in a Christian school, one of our first topics in almost any American History class I took was whether or not the United States was founded as a Christian nation. It's been several years since then, and I remember discussions and a strong bias coming from the fact I went to a Christian school, emphasizing the fact that many of the founding fathers were Christian.
So, in reality, was the United States founded as a Christian nation?
No. First Amendment guarantees freedom of religion.
The Constitution is the United States' governing document. It makes no reference to religion, save for "no religious tests for office" (making it explicitly illegal to restrict government offices to Christians), so no, the United States is NOT a "Christian Nation."
The founding fathers were actually not largely christians. Jefferson, for example, rejected the entire christian system as well as the idea that the bible is the word of god.
The founding fathers were diests, not christians.
No. It was founded by people who came from a culture which had some of its historic and cultural roots in Christianity but ultimately was an Enlightenment Republic founded largely by deists and secular Christians (with a few exceptions) and was based around the people being sovereign, not any deity.