But Americans shouldn't just think more about Canada. They should consider building on the two countries' free-trade deal and forming a more perfect North American union. It is past time for the U.S. and Canada to eliminate their border—either by creating a customs and monetary union or, more radically, by merging outright into a single nation-state or a European Union-style partnership.

Such a merger makes perfect sense. No two countries on Earth are as socially and economically integrated as the U.S. and Canada. They share geography, values and a gigantic border. Their populations study, travel and do business together and intermarry in great numbers.