The force that founded America was spiritual, indeed evangelistic. Landing at Jamestown in 1607 Pastor Robert Hunt erected a cross, took communion, and covenanted, “We do hereby Dedicate this Land, and ourselves, to reach the People within these shores with the Gospel of Jesus Christ, and to raise up Godly generations after us, and with these generations take the Kingdom of God to all the earth. May this Covenant of Dedication remain to all generations, as long as this earth remains, and may this Land, along with England, be Evangelist to the World.” In 1620 — blown off course, but not off mission — Mayflower Compact, “…for the glory of God and the advancement of the Christian faith.”
The Pilgrims “advanced significantly the Bible’s message that God’s kingdom is irrupting into the world for his glory and our good.” –Dr. Bruce K. Waltke, “An Old Testament Theology.”
As the nation survived and became independent, the Founders established America legally as a Christian nation at the state level, rather than the Federal (details here).