When we succeeded in winning the Cold War, escaping a nuclear Armageddon that could have killed us all, the U.S. inevitably had a serious problem about an encore: what now for our place in the world?

Terrorism is really the only existential threat to America as we know it - as a free country that plays a leading role in the world.

The absence of a focal enemy, which is what the Cold War had provided; the complexity of the developments that are occurring that mean that the world is just extremely complicated - lots of different and competing stories and strands; the continuing reality of megaterrorism; and the dysfunctionality of our politics that has neglected the foundations of the U.S. role in the world; have altogether left us somewhat confused.

Given that the Al Qaeda core has been significantly destroyed or disabled, and that the leadership seems to be essentially on the run or in hiding, it would lead me to think that probably it is one of the less centralized groups that might be the greatest danger.

I think the election of Trump was an expression of what happens in ruling powers as they become alarmed.

When we succeeded in winning the Cold War, escaping a nuclear Armageddon that could have killed us all, the U.S. inevitably had a serious problem about an encore: what now for our place in the world?

And I hope that we can learn the lessons of the past in looking at the current challenge that China poses to a ruling America.