The word “federalism comes from the Latin “foedus” meaning covenant, compact, or treaty. One of the arguments that the United States was a Christian nation comes from the concept of federalism being derived from the teaching of Scripture. Heavily influenced by John Knox and his Book of Order, America may have been founded under the principles of “covenant” with the God of the Universe. It was to be a government by representation as indicated in Deuteronomy 1:13. Here, Moses reminded the Israelites of choosing wise and discerning men to represent them. The government of the United States would be a government “of the people, by the people, and for the people.” Without wise and discerning men to represent us, we will become as bait for the wolves. In fact, Thomas Jefferson once said, "If a nation expects to be ignorant and free, in a state of civilization, it expects what never was and never will be." In other words, an ignorant people have never been free.
The three divisions of government sound very similar to Isaiah 33:22, which describes God as a judge, lawgiver, and king. Hence, the judiciary, the congress, and the executive branch of government reflect various aspects of the character of God. The Scottish Covenanters had a great influence in the founding of American government. Part of it came through the teaching of John Witherspoon who was President of Princeton during the Revolutionary War period of America. He influenced two thirds of the signers of the Declaration of Independence and many others who became part of the integral founding and ruling of Colonial America to include James Madison, a Virginian sent to Princeton to be educated under Witherspoon.
The dual nature of government in obeying God and magistrates was a Covenanter principle. The principle was derived from Matthew 22:38-40 in which Jesus said that the foremost commandment is to love God with all your heart, soul, and mind; and to love your neighbor as yourself.  Since Jesus was King over all peoples and nations, subjects answered to Him. Obedience was to God and the men that were appointed by God to run the nation (Rom. 13:1ff). The idea of Church and State coexisting for mutual benefit was derived from the Covenanter principle known as the “Mediatorial Kingship of Jesus Christ.” It could be diagramed as follows:

                                                         CHURCH                      STATE

God in Christ is the ruler of all nations (Psalm 47:8). Christ does not cease to rule over the state because governments fail to recognize Him. He still remains King of the Universe and laughs at unbelieving nations, holding them in derision (Psalm 59:8). The State exists because of Him who respects no nation (Isa. 40:17). Those who are magistrates have an obligation to rule under Him according to His dictates, which are found only in Scripture (Rom. 13:1ff). The State therefore exists to rule for the common good and to protect the Church and its teachings about Christ and religion. The Church exists to teach the State how to rule for the common good in accordance with the principles of Scripture. The Church is charged by Christ to teach the values and morality of the Christian religion and the State is to protect the right to do so. Civil government therefore is a divine institution and is subject to the law and authority of Christ.  Nations claiming to be Christian have by covenant declared so.  Christ has authority over nations, governors, and legislatures, and it is their duty to serve and obey Him.  Ignorance of the Word is no excuse.
It is sad that our own United States no longer recognizes Him who is King over all nations. We may pay a price for relegating the Lord of the Universe to a position of scorn and disparagement. A lion has gone up from his thicket, a destroyer of nations has set out; he has gone out from his place to make your land a waste; your cities will be ruins without inhabitant (Jer. 4:7 ESV).