This book The Great Division is not directly referring to America as a nation. It concerns the Church, the followers of Christ. However, our nation has never been so divided since its inception. Though our founding Fathers may not have been godly men in all their ways, they did acknowledge the Greater and credited Him as the source of all our blessings. They invoked His blessing before going into battle, before writing the Declaration of Independence and the Constitution, and before enacting new laws, etc. As a result of these prayers, this nation has been blessed and has prospered.
However, the great division to be concerned with is the one the Apostle Paul talks about in II Thessalonians 2:1-12.
In v.3 Paul tells of the falling away of the Church you currently see in which the antichrist of Revelation will be revealed.
In v.7 he tells us that the Holy Spirit has been restraining the lawless one (the beast, the antichrist) from coming into power.
The Holy Spirit has maintained that “hedge of protection."
However the falling away of the Church in recent years has been the reason that hedge of protection has been lifted.