The idea of such a bank has been around since the 1990s but has never gained significant attention until now. In March a bipartisan bill was introduced in the Senate that gained the support of the US Chamber of Commerce, America’s leading business lobby, and the AFL-CIO, the country’s largest labor federation — two groups on opposite sides of most debates. The BUILD Act, proposed by Sens. John Kerry, D-Mass., Kay Hutchinson, R-Texas, and Mark Warner, D-Va., would create a national infrastructure bank that would provide loans and loan guarantees to encourage private investment in upgrading America’s infrastructure. There are...