Look at Japan, where gross domestic product today is less than two-thirds of what most observers predicted a generation ago, even though interest rates have been at zero for many years. It is worth emphasizing that Japanese GDP was less disappointing in the five years after the bubbles burst at the end of the 1980s than the US GDP has since 2008.

There is increasing concern that we may be in an era of secular stagnation in which there is insufficient investment demand to absorb all the financial savings done by households and corporations, even with interest rates so low as to risk financial bubbles. Raising demand through greater infrastructure investment is an antidote for such malaise as well as a source of better employment and economic growth.
We live in an ever more interdependent and competitive world. Savings can flow into any country. The fruits of research and development flow globally. Many iconic American companies now earn less than half their profits in the United States.
But one thing that is inherently immobile is our infrastructure. When we put money into strengthening our infrastructure, essentially all of what we spend stays in the United States. Once in place, all the benefits of the infrastructure go to Americans.