“Now these are the nations which the LORD left, that He might test Israel by them, that is, all who had not known any of the wars in Canaan (this was only so that the generations of the children of Israel might be taught to know war, at least those who had not formerly known it).” (Judges 3:1-2)
This new generation of Israelites under Joshua had never known war. Even though God promised them the land of Canaan, God intentionally left some pagan nations in Canaan so that this new generation would have to learn how to fight if they were going to possess their promised land.
Could it be that God has allowed the opposition America is currently facing in order to teach this current generation of Christians spiritual warfare? Have you been taught to know war? Are you going to sit by and let America be taken over by pagan philosophies or go to battle on behalf of America?