The start of negotiations for a free-trade agreement between the European Union and the United States - officially called the Transatlantic Trade and Investment Partnership (TTIP) - marks a key turning point for the EU and world trade. It also reinforces both sides' shift away from multilateral trade policy in recent years. That might be the right move for America, but it could spell serious trouble for Europe.

Over the past half century, the EU, which represents only 7 percent of the global population, has managed to maintain an exceptionally strong trade position, despite the rise of emerging markets like China. So, while the US and Japan have seen their respective shares of global exports fall, the EU's share has remained stable, at around 20 percent.

Indeed, EU trade power contrasts sharply with the perception of a weakened Europe. Most important, Europe was able to achieve it only by investing heavily in a multilateral trade system through the GATT and then the World Trade Organization.