The 2,000-mile U.S.-Mexico border is a pure disconnect, at least in terms of transportation. Both countries have highway routes designed long before the possibility that the economies of the two nations would someday integrate under a North American Free Trade Agreement. The result is that NAFTA land trade must zigzag through obstacle courses as raw materials and components go to factories and final products are shipped to markets. The best-positioned border-crossing ports, such as Laredo, are overcrowded. The others are underused. The governments of both nations understand the competitive necessity to build better highway connections. The cost is prohibitive, however,...