What were the principle challenges to the international order in the Post-Cold War world

What were the principle challenges to the international order in the Post-Cold War world

Those references can be useful:
Henry Kissinger, Diplomacy, chapter 30?
G. John Ikenberry, ‘The Restructuring of the International System After the Cold War,’ in The Cambridge History of the Cold War, Vol. 3.?
Francis Fukuyama, ‘The End of History?’ The National Interest (Summer 1989).?
Samuel P. Huntington, “The Clash of Civilizations?” Foreign Affairs, (Summer 1993).?
John Mearsheimer, ‘Back to the Future: Instability in Europe after the Cold War,’ International Security,
Vol. 15, No. 1. (Summer, 1990)?
William C. Wohlforth, ‘The Stability of a Unipolar World,’ in Karen Mingst and Jack Snyder, eds., Essential Readings in World Politics (2001), pp. 157-173.?
Samuel P. Huntington, “The Lonely Superpower,” Foreign Affairs, (March/April 1999).