Let every soul be subject unto the higher powers. For there is no power but of God: the powers that be are ordained of God.---Epistle to the Romans, 13:1
America could hardly be a "Christian nation" founded upon such an unBiblical act!
However, in this 1818 letter looking back on the Revolution, John Adams describes the colonists' theological justification for the war: They didn't fire King George, he quit.
But what do we mean by the American Revolution? Do we mean the American War? The Revolution was effected before the War commenced. The Revolution was in the minds and hearts of the people, a change in their religious sentiments of their duties and obligations.
While the king, and all in authority under him, were believed to govern in justice and mercy according to the laws and constitution derived to them from the God of nature, and transmitted to them by their ancestors, they thought themselves bound to pray for the king and queen and all the royal family, and all in authority under them, as ministers ordained of God for their good. But when they saw those powers renouncing all the principles of authority, and bent upon the destruction of all the securities of their lives, liberties, and properties, they thought it their duty to pray for the Continental Congress and all the thirteen state congresses, etc.
There might be, and there were, others who thought less about religion and conscience, but had certain habitual sentiments of allegiance and loyalty derived from their education; but believing allegiance and protection to be reciprocal, when protection was withdrawn, they thought allegiance was dissolved.Indeed the Declaration of Independence reads:
2) "He [King George III] has abdicated Government here, by declaring us out of his Protection and waging War against us."And so the colonists--in harmony with Romans 13--transferred their allegiance to the duly constituted authorities, those of their state governments, and of the Continental Congress. Parliament was not their constituted government—the colonists did not and could not vote for or against them.