In his 1996 State of the Union Address, then President Clinton said twice “The era of big Government is over.” Clearly it was not. While government spending ebbs and flows, big government continues to be a feature of American society.
If I were President I would claim the “Era of big (civil) Infrastructure is over” in the US. Not that we don’t have big infrastructure, we do, and it isn’t going anywhere soon. The size of the paved area in the US is on the order of the State of Virginia. That’s pretty big, and just looks at one measure of one infrastructure (admittedly a large one).
Once upon a time we did deploy big infrastructure. The railroads in the 19th century, and the interstate in the 20th were BIG. Turnpikes and canals were other large technical systems of the 19th century, as were the US Highway system, airports, container ports, and the like in the 20th. But they have been deployed, and many of them area already shrinking.
Instead, because the existing infrastructure systems are mature (built out), they need little expanding (and likely some contracting).
Certainly there are potential new infrastructure for surface transport. The most widely discussed would be intercity High Speed Rail and urban transit projects. Similarly there are proposals for water (rebuilding the water and sewer networks) and for energy (massive investment in renewables as well as smart grid technologies). I think the transport investments are unlikely, the water investments are mostly piecemeal replacements, and the energy investments will be a set of many small, decentralized power generators rather than large facilities. In short change is likely to incremental rather than comprehensive.
In part the question turns on what you mean by “Big”, and I think we mean system level deployments, like the interstate, or a national HSR network, and not individual segments that are adding to an existing system or replacing an existing system element in-kind with some added functionality.
On the transport side, there is little interest in large new systems. The last great window for high-speed rail was the 2009 Recovery Act, which did not achieve that aim. Seven years in and there is no actual high-speed service to show for it. Even if the California line were ever opened, we are decades away at the earliest from the onset of a national network in the US.
Proposals for new Interstates appear from time to time (like this for I-87: [10 points if you knew that was Norfolk to Raleigh without looking it up]), and occasionally one actually opens, and even a second or rejuvenated Interstate 2.0 system has been proposed, but again there is no strong push for such a thing, and the advent of new technologies gives such proposals a ghost-like feel.
There are new systems emerging. The internet and wireless telecommunications are pretty important. Combine these with transport and we can construct an on-call ride-hailing system that has updated the traditional taxis. This may eventually become substantial with Autonomous Vehicles. But this latter element is not a conventional physical infrastructure investment (not much of one, some servers, some software), rather it redeploys existing (and soon new) vehicles in a useful way.
The new information-enabled systems that ride on-top of the classic physical layers are the products of Electrical Engineers and Computer Scientists, not great Civil Engineering works. We can imagine some things that might become useful. For instance we can think of space civil engineering, things like Space Elevators and Dyson Spheres. But these are not on the near horizon.
Unless we can find an infrastructure that increases connectivity massively the way the railroad and the interstate did (doubling speeds, e.g.), there is no point in spending resources for that given the increasingly high costs and diminishing returns that civil infrastructure faces. We have enough trouble maintaining what we have with its proven connectivity (or lack thereof), the value of future infrastructure systems is speculative at best.