Isolationism, unfortunately, is not limited to one policy or one party. Liberals have been skeptical of free trade for decades now. Less than 10 percent of House Democrats voted for the Central American free trade agreement in 2004. And Democratic politicians, including President Obama during his re-election campaign, routinely hype the danger of multinational firms outsourcing jobs.

Before the Fall, a Wall

The psychological impulse to protect a nation's wealth and culture from foreign contamination is an example of what behavioral economists call "loss aversion" - the idea that people are more concerned about what they might forfeit than gain from change. History tells us that with great power comes great loss aversion.

Take the fate of Ming China, the world's most fabulously wealthy civilization in the 15th century. The empire cut itself off from foreign trade after the 1430s, an action urged by Mandarin bureaucrats in order to clip the power of the merchant class, their rivals at court. Court intrigue is also revealed by the extension of China's Great Wall, and the abrupt termination of the voyages of Admiral Zheng He, both reflecting the Confucian attitude that foreign barbarians offered nothing of value. The following centuries saw China transform into a weak and isolated time capsule.

Or consider the Berlin wall, the manifestation of the "Iron Curtain" that hid the stagnancy of Soviet power from 1961 to 1989. Unlike Roman or Ming walls, the communist walls blocked emigration rather than immigration, which is an even more destructive strain of inwardness. At least 246 East Germans were killed trying to escape to West Berlin, but millions more were imprisoned in a failing communist economic model. In its defense, GDP per capita in the Soviet Union rose from $4000 to $7000 per person during the final decades of the Cold War, but that compared poorly to British incomes, for example, that rose from $8900 to $16,400.

Britain itself is a particularly interesting frontrunner to the U.S., but not because of its reputation as the birthplace of free market economics. During the peak years of empire, Britain's Parliament neglected to extend citizenship to its colonial subjects not once, but twice. The first time it fumbled a continent full of human capital was in North America in the 1770s. The second time was in the 1880s, when a fear of declinism stymied progress.

Prime Minister William Pitt (the elder), who led Britain during the 18th century, recorded his own expansive dream of a Greater Britain in his personal papers. Pitt's "scheme for better uniting" proposed that there be four members of Parliament to represent Virginia, four for Pennsylvania, four for Massachusetts, three for Jamaica, three for New York, two for Canada, and so on. Adam Smith's The Wealth of Nations made the same appeal. And yet it never came to pass. In 1707, the English Parliament added Scotland's representatives to its chamber. Northern Ireland was given direct representation in 1800. Conspicuously absent was an offer to the Americas during the decades in between, or the Indians later.