Just because our infrastructure is lousy doesn't mean "underinvestment" is the cause. However, you measure it, American infrastructure has become extremely expensive to build. Countries with nice infrastructure---like Japan and European countries---can also build it much more cheaply.
A number can be small because the numerator---the total amount of funding---is small, or because the denominator---the amount of infrastructure purchased per dollar---is large. In the US, it's mainly that the denominator is large. And because the denominator is large, we choose not to make the numerator as big as it could be.
Also, the point about public transit is a real cheap shot against Republicans. Public transit accounts for a small percentage of total infrastructure investment. Even if it were doubled, this would have almost no impact on our infrastructure budget. And much of what transit is built now fails to pass a benefit-cost test. Look at BART's extension to Livermore. Look at the new Bay Bridge span, which now has a whole book about it
http://www.citylab.com/politics/2015/10/from-250-million-to-...
A number can be small because the numerator---the total amount of funding---is small, or because the denominator---the amount of infrastructure purchased per dollar---is large. In the US, it's mainly that the denominator is large. And because the denominator is large, we choose not to make the numerator as big as it could be. Also, the point about public transit is a real cheap shot against Republicans. Public transit accounts for a small percentage of total infrastructure investment. Even if it were doubled, this would have almost no impact on our infrastructure budget. And much of what transit is built now fails to pass a benefit-cost test. Look at BART's extension to Livermore. Look at the new Bay Bridge span, which now has a whole book about it http://www.citylab.com/politics/2015/10/from-250-million-to-...