American christians , if the US was founded as a christian nation?

Yes

The Constitution was not a founding document. The United States existed as an independent nation for several years under the Articles of Confederation prior to the ratification of the Constitution. Each state was free--and continues to be free--to define itself as a religious or non-religious entity, and some do profess to be Christian.

The Constitution reflected the views of its framers that the United States should not have a state religion. The United States was formed of entities and individuals who were Christian. Many of the founders were deeply intellectual people who may have defined themselves as deists rather than Christians, yet many of them were also churchgoers. Our laws are based on Judeo-Christian principles.

While I believe the Constitution is a unique and wise document it is not fundamentally a founding document. The Declaration of Independence, which does mention God, is the closest thing to a founding document we have. These two documents should be considered together in defining our Republic.

"He is mentioned in [...] the Constitution (referred to as divine providence)"

Of what country? Neither of those two words is in the Constitution of the United States of America.

You forget Thomas Paine, for one.

I suggest you take a history class and learn to read.

"Have you ever actually read the Declaration of Independence?"

Yes, I have. Unfortunately, the passage you cite has nothing to do with the separation of Church and State. It has to do with the separation of the colonies from Britain.

Have you ever actually read the Declaration of Independence?

" When in the Course of human events, it becomes necessary for one people to dissolve the political bands which have connected them with another, and to assume among the powers of the earth, the separate and equal station to which the Laws of Nature and of Nature's God entitle them, a decent respect to the opinions of mankind requires that they should declare the causes which impel them to the separation."

It was our forefather's desire to separate "Church" and "State" to keep religion from influencing governmental law.

Hell no. If America was a Christian nation I'd be in jail.

People in America have religious freedom.

No, America is secular, hence why we have freedom of religion. It just so happens that most people in America are Christian.

Ironically it was founded by people who left England in order to cherish their religious freedom. So now they (and we) are stuck with such nonsense as Islam (and extremism of course).

He is mentioned in the Declaration (as the Creator) and the Constitution (referred to as divine providence)

The kept it generic....but He's there, because he was in almost all their hearts with the exception of Franklin (who was a reprobate) and perhaps Jefferson