America has reached a crossroads. And Barack Obama has a difficult road ahead, because it is his task to lead the nation into a world of limits. From the very beginning, Americans have seen their country as a land of infinite opportunity. And, as long as the frontier beckoned, anything seemed possible. It was the frontier, after all, which nurtured Abraham Lincoln.

Now another president from Illinois has told his fellow citizens, as Richard Cohen writes in The Washington Post, that “the American century is over.” That knowledge will be a bitter pill for many. But America has been here before. Cohen writes:

I have heard this speech before. I heard echoes of Richard Nixon explaining “Vietnamization.” Gonna turn the war over to our stolid allies. We put them on their feet. We trained them. We supplied them. We schooled them at our elite military academies. They looked splendid in their uniforms. But when the U.S. pulled out, South Vietnam collapsed. It will happen again in Afghanistan. I think Obama knows that. He fought this war — authorized the West Point surge — because he did not know how to get out. Now, he does. As any previous president could have told him, it’s by getting out.

Some will see the retreat from Afghanistan, like the withdrawal from Vietnam, as a defeat. But the Vietnam War was a mistake. It was the wrong response at the wrong time. After 911, the enemy was Al Qaeda, not the Afghans; and Iraq had nothing to do with the attack on the World Trade Center.

It has taken awhile to put Vietnam in perspective. And it will take time to see the last decade — with the benefit of hindsight — clearly. Recognizing the finite nature of one’s circumstances is the beginning of wisdom. And with that recognition comes another kind of wisdom. We are not merely citizens of the country of our birth or our choice. We are also citizens of the world — a world that has always been finite.

Owen Gray grew up in Montreal, where he received a B. A. from Concordia University. After crossing the border and completing a Master’s degree at the University of North Carolina, he returned to Canada, married, raised a family and taught high school for 32 years. Now retired, he lives — with his wife and youngest son — on the northern shores of Lake Ontario. This post is cross posted from his blog.