What were the most distinctive principles of the new confederate government?

the continuation of slavery is the answer

Prior to 1867 the US had expanded coast to coast acquiring the continental US. Foreign policy was isolationist. 

Causes for change: modeling Great Britain in becoming a modern nation, 1890 Mahan's book on the need for sea power and naval forces,1893 World's Fair and Frederick Jackson Turner Thesis declaring the closing of the frontier, interest in Cuba and the rising independence movement against Spain. 

Internationalist view begins with US involvement in Cuba assisting their independence from Spain. Under McKinley, the US became imperialistic increasing their role in the world.